I'm not sure if some of the other codes for Exp. Pts actually work, or not just yet...however I know one that does.
I also know how to garuntee 9999 points for Tech, Ether and Skills. Use them or not its all up to how you game and how much you wanna experiment.
--Now, for ungodly amounts of exp (or about 9999 with three party members to lvel up, minus those exp that go to your reserves) use this code. If used at begining of game, with ONLY Shion on Woglinde, you can easily get Lvl 49 in one battle!
However, the following code WILL make any character (regardless of how many, combatants AND reserve) Lvl 99. It is best to use this code in the following sequence:
1: On Woglinde. Save game and deactivate code as soon as possible (just in case). Be sure to max out Shion and KOS-MOS' stats with tech points ASAP.
2: Pleroma; only AFTER you have maxed out all of Ziggy's stats (including HP) but BEFORE you free MOMO. (trust me, there is a reason). Now save and disable code.
3: Pleroma: Now thqat you have freed MOMO with the EXP code OFF, wander around a while until you max out all her stats using T.Pts. Save in the Pleroma control room (or wherever BEFORE fighting the next boss), activate code and face the boss.
4: Elsa: After the scene where you pick up Ziggy and MOMO, but before you head down to B1, max out chaos's stats. Save, activate code, and procede to make 5/6 of your characters Level 99. You'll like the stats now that you can kill most Boss enemies with just one basic attack!!
Okay, with all that done make sure you deactivate that code BEFORE you go shooting enemies with Jr. Best idea would be to save before facing the Domo Carrier and kill the code then.
From this point on you won't need it since the only one getting any Exp will be Jr. from here on out.
Just make sure to have plenty of Escape Packs for him to use (about 45 minimum) to max out his stats and enjoy the rest of the game.