I completed the game earlier today and all of the extra stages (except the 31 daily stages, because that's just unreasonable), and decided to mess around with the codes. In case anyone cares, I'll be talking about some things.
It's better to use the infinite EXP code at an end game stage, because it seems that how fast the exp bar fills is coded in the system depending on the locale. If you did it at the first stage in the game, it would take you like 10 minutes for a level up, but if you did it at the end of the game, it would only take a minute or so to fill up. Sadly there is no way to speed up the leveling. You'll be waiting quite a bit of time to get everyone to level 50.
1 hit ko cpu code seems to mess up the timer bonus. If you want rainbow S rank, just use the 20 plates code and spam click on plates like 10 times. It also causes the puzzle hut robot to act weirdly. You have to have the infinite timer on if you use the 1 hit kill or 20 plates code on the bot, otherwise he'll automatically kill you as soon as the next stage starts for some reason. In case anyone was wondering, max level in puzzle hut is 99, and when you hit 99, it just rolls back to 99 every time you beat a stage. You only need to get to level 31 for the Triumph. I didn't know how low the "real" timer gets reduced at level 99, but I assume it's comically impossible.
There doesn't seem to be a limit for stacking plates under the infinite time code. I got up to 180 before I missed a link. I think this code needs to be on if you use the 20 plate stack code. If you just hang around and do nothing while the 20 plate code is on, you'll hear the 7 second timer counting down. When it hits 0, the game crashes.
Max possible HP for Musashi is 23500 and max possible attack is 150. You have to be level 50 and have used 15 each of the cans of strength and stamina. After you use that many, they get greyed out.
The most HP you can give your sprites through guardian charms is capped at 2500 I think. After 5 of the large charms (+500 hp), you can't raise the HP anymore and the sprite is greyed out. Max HP for sprites is around 4000-5000, depending on who it is.
All of the skills for all of your sprites can be maxed with just the two sets of 80 skill charms. You'll have a few leftover.
I don't know if there is a limit for using party charms on a sprite, but I used 90 on Jinrai and he was still selectable. The smiley face for him on the party charm page was "Hot Pink." I'll just assume that is the max. I got to the "hot pink" smiley after around 40 party charms.
Final notes: True 100% for this game is utter and absolute bullshit. If you were to try and get it legitimately, and you played this game 24/7 from release date back on June 8, you probably still wouldn't be done. For one, you can't, because of the 31 daily battles at the very, very end. That puts the earliest a person who bought the game on launch could get 100% at July 9th, assuming they didn't go insane from grinding exp. Also, the EXP requirements for maxing everyone is way past the outer reaches of space. So if you see anyone with rank 10, they cheated. Also LOL at puzzle hut. Good luck getting 30 without cheating.