Some notes about this mod:
First, items multiplier DOES work, just not how you think. First, it only works on items gained from chests, glitter-points, similar interaction points, and sometimes from items gained by conversations/messages (depends on how gaining the item is coded). It does NOT work on enemy drops. It also does not work on Git unless that Git is found in a chest. Second, it is not actually x25, x50, x255, but it sets the amount gained to the chosen multiplier. So if set to x25, if you pick up x1 item, you get 25 of it, if you pick up x3 of an item, you get 25 of it. If you open a chest with 50000 git, you get 25 git. Note that the change in items gained is not displayed in the pickup message, but is reflected in inventory.
Having this active while doing the Mementos Dungeon will cause all chests to only give the set amount of Decayed Thought Leaves, making it almost impossible to gain a worthwhile amount of them if not set to x255, and even then it won't always be worth it. This also applies to chests that contain similar items, such as Atlantis Pearls, but their primary source is battle drops, which it does not effect.
This cheat does effect Chaos Crystals/Drops, so you want to turn it to x50 or x255 when fighting Horrors that drop 50.
Picking up the following items while having a Pick Up Item multiplier active will break the game, preventing you from progressing the story and forcing you to restart with a new account if you wish to continue (There may be other key items that break the game, but these are the ones I'm aware of):
Stone Memory Music Box - Chapter 21: Palsifal Palace, underneath the King's Pillow
Specter Palace Key - Chapter 52: Specter Palace, 2F, Western Side, room behind shell shield
Jyomodo Key - Chapter 58: Funeral Cavern B2F - Infront of the altar, northern-most section of map
Dungeon Key - Chapter 72: Land of Ro: Dungeon Ruins 8F (May also include the items picked up from fainted guards)
Small Bomb/ID Card - Future Garulea Continent - Angal - Researcher Shop/Sky Fortress Eeza - Shop (Prevents progressing in Future Garulea Continent Another Dungeon, not Main Story Progression)
There are quite a few other things that will break if you have this cheat active, but none of them are game breaking. If you want to be safe, just assume that Key Items will break the game if you have multiple copies. (While this is not true of all Key Items, to my knowledge ONLY Key Items break something when there are multiple copies). Below I am going to list additional issues caused by x25 Items as I find them.
Toto Dreamland - Hide 'n' Seek Totos - When collecting rewards for this objective, if x25 items is active you will only be able to collect one reward. You can activate x25 Items when you only have one reward to claim remaining and you'll receive 25 of that one.
Acteul - Tales of Story - Cooking Minigame - If you have x25 items active when accepting a reward for cooking an ultimate meal it will not let you accept more rewards after that one. I'd assume you can do like above and activate x25 Items for the last item you collect.
Complex Dream - When picking up the Key in the Tavern, you will not be able to pass through the locked doors if you have x25 items active. This will cause you to miss a Scarlet Meteorite, but as x25 items works for many of the Scarlet Meteorite pickups so it is mostly irrelevant. This does not block progression in any way.
Past Garulea Continent - When getting the Maiki Weapons from the ***u Riddles, if you have x25 Items on when you answer the ***u you will not be able to complete the final riddle. Similarly, you will not be able to turn in Key Items picked up to answer some of the ***u. I recommend while obtaining these weapons, turn off x25 Items. Turn it back on during the Boss Battles associated with each weapon so you get 25 of the weapon (if you want) and turn it back off after the battle.
As a rule of thumb, since gaining increased amounts of only key will cause issues, I recommend checking wikis for locations of key items so you can turn off the cheat before gaining them.
NOTE: As I've seen several complaints about obtaining Chant Scripts, I thought it would be useful for me to list the locations where you can get them and the x255 Cheat works on them:
Miyu Story; Chapter 5 - Chest in Secret Area
Miyu Story; Chapter 6 - Throwing axes into the pool in the Secret Area
Ciel Story; Chapter 5 - Chest in Secret Area
Ciel Story; Chapter 6 - Giving the Robodog in the Secret Area bones
Time Mine; Mine 3 - Chest (From Entrance: First North, First North, First North (Need Bomb), Use Ladder, Use Rope, First North (Need Bomb), First North (Need Bomb), Use Lantern, Behind Horror)
Tales of Time; Citadel of Time Lower Sector - Chest
There's a low chance of finding on in chests in any VH Dungeon or Otherlands. Also in Ruins of Rucyana Treasure Room White Chests always have one. The Garulea Continent also has a low chance of finding one in Chests, though notably, the Boss Room of the Satellite Stadium has a 10% chance of having one.
So that's 6 guaranteed (ie 150 Chant Scipts) and then I'd recommend farming Future Garulea Continent - Satellite Stadium (Better chance) or Ruins of Rucyana (Faster Runs) if you need more.
65K Gold Per Battle is actually 65,025 Git per Battle. Why the extra 25? No idea, but git is git, so whatever. This cheat doesn't hurt anything I've encountered. Like the Item Pickup, this change is not reflected in the git gained message shown, but is reflected in your inventory.
Install Max Lv is actually Instant Max Level and will immediately max out the level of all members of your party after one fight. It does not hurt to leave it on. It will not level units that were not in your party during the fight, so you'll have to switch units for that. This cheat doesn't hurt anything I've encountered, although it does not work in Cat Battles.
God Mode prevents changes to your party's HP. You can still be affected by Status Affects, such as Poison, Sleep, Pain, or Stun, but will not take damage from them. This also means you cannot recover HP during battles through Healing effects, though Backline units will recover. Outside battles, your party can recover by eating food or resting as normal. This is noteworthy because of the Grasta Enh. Dmg at Max HP. If you have a unit that increases Max HP, you will not be able to heal to your new maximum while this cheat is active, thus preventing the grasta (or skills with similar effects) from working. You need to turn this off during fights that you are "scripted" to lose, such as the first battle against the Beast King in Baruoki Village when Feinne is taken. It will not hurt anything if you engage the battle while God Mode is active, or even if you survive the "instant kill" attack, as the opponent will just repeat their cycle as if the fight just began after that, including dialogue. Worst case scenario, you can just close your game and open it again, as Autosaves are before/after each fight, not during them. I THINK you cannot kill these opponents, though if you could/did it would likely break the game, hopefully before an autosave. I don't recommend testing it. Don't worry, x20 damage will not allow you to one-shot such opponents as they have an unusually massive health pool. God Mode does not work in Cat Battles.
Dmg Multiple multiplies your PHYSICAL damage by whatever it is set at, but has no effect on Magical Damage. It does not multiply opponent damage. In Cat Battles, the multiplier does apply to both your damage and opponent damage. I've found that if you are higher level than the opponent, you can safely set it to 3 to speed up Cat Battles. If your damage would be over a certain amount, you don't deal any damage. This amount seems to be over 250 million and less than 1 billion.
The Hide/Kill (Hold) Button makes the icon disappear if you press it, but does not remove it from the game. Just tap the location the icon was at to open the menu again. If you hold down on the button it shuts down the mod, but it will restart when you launch the game again.
The Minimize Button does not close the mods, it just closes the menu, collapsing back down to the little icon.
There is no usage of this mod that I have found thus far that has caused a ban.
Note that while using the modded APK you cannot make purchases of microtransactions for Paid Chronos Stones or Subscriptions. You must switch to a non-modified APK to do so. Attempting to make such purchases will not cause a ban.
If you are aware of other key items that break the game, let me know and I'll add them to the list.
Edited to update Dmg Multiple
Edited to update x25 Items
Edited for Cat Battles
Edited for changes to x25 items
Edited for Complex Dream x25 items
Edited for Grammar and minor clarifications
Edited for changes to x25 items
Edited for God Mode clarifications
Edited for x25 Items clarifications
Edited for Mod Changes