A: Gogeta requires SSJ Goku AND SSJ Vegeta to be unlocked first. Use the cheat code that unlocks "Alternate Costumes" as well. Some cheat codes only unlock base roster, not fusions.
: Extract the downloaded ZIP file and move the folder (e.g., ULUS10234000 ) into the SAVEDATA directory. dragon ball z shin budokai 2 ppsspp unlock all characters
If you want to avoid cheats entirely (to keep the game stable or because you dislike hex editing), download a "100% savedata" file. A: Gogeta requires SSJ Goku AND SSJ Vegeta