There's nothing specific against cheat codes that should make the Sephiroth battle impossible. However, depending on your cheat choices, you may make the battle more difficult. I'm assuming the one that would destroy you is Safer Sephiroth, the one-winged angel form. In addition to all of its special abilities, it also has the following two bonuses that you probably triggered in your cheat methods compared to your non-cheating methods.
- Each character at Level 99 (except Aeris) adds 30,000 max HP, 2 Attack, 20 Def, 5 Magic, and 16 MDef.
- Casting Knights of the Round on Jenova∙SYNTHESIS (who you fight just before Sephiroth) adds another 80,000 max HP.
Numbers were pulled from the Final Fantasy Wiki. The previous form of Sephiroth also gains increased HP from level 99 characters and using KotR on Jenova, but not nearly as much.
The total boost he can reach for HP alone is a factor of 5: from his normal 80,000 to 400,000. His other stats, of course, are also improved, notedly with a strong emphasis on defense. This is what makes an under-level party (and one who failed to acquire Knights of the Round) actually easier to face off against Sephiroth. I know I managed to defeat him on my first playthrough at subpar levels (Cloud only know his Meteor limit, Vincent his second, and I had Cait Sith with Dice... I don't even know what I was playing at that time).
The only other factor you may have run into is that in using cheat codes you might've slouched in better party upkeep, such as by forgetting to equip proper status defense (he has a lot of those) and buff the party consistently. Past these things, though, using cheat codes shouldn't have any direct effect.
A note should be made that the faux final battle that ensues afterwards is cited to have some interesting effects when using cheat codes, none of which cause Game Over though. It does reinforce that cheat codes themselves shouldn't have affected the previous fight.
The best place to level up in ff7 is the Swamp area in the Northern Crater, it is in the final dungeon of disc 3, but is by far the best place to level. If you are leveling to fight the optional weapons (Ruby, Emerald, Ultima) then i would just progress until you can level here.
The enemies you want are Movers, they have little (0?) exp but insane AP and are easily killed, and Magic Pots give great exp and ap, but require an elixir to kill (must give it to them first). You can steal elixirs from Gighee Which is also found in the swamp.
General method in the swamp is Steal Elixirs from Gighee (Or just use W-Item Duplication on Elixirs), use Elixirs to kill Magic Pots. Also, while hunting these two be sure to kill Movers great AP, and just run from everything else. This place is so good I usually end up putting my save crystal here.
If that isn't preferred, where you currently are I would recommend Mideel area, the Spiral and Head Hunter (found in forest) enemies give good exp and ap for that part of the game.
If you want to auto level you can fight the Midgar Zolom (Just stand inside the Midgar Swamp with X taped down, turbo might be needed). You can also auto level on certain beachs by holding down, your character will run up and then down the beach in constant motion. Again having X taped down will auto kill monsters. For these methods you might want to consider Sneak Attack materia in your setup.
Hope this helps
Best Answer
You can't find a Golden Chocobo, you have to breed it. The process is time consuming and exhausting, so prepare yourself for hours of birds mating and races (because you have to train them too).
The complete process can be found in this guide explained quite in detail.
To sum it up you have to:
Inbetween you'll have to find various objects to feed to your chocobos, and various things are completely random (such as the gender of the chocobo you'll get). Be patient and your reward will come!
Oh, and obviously you can use it in the Golden Saucer, it's simply the best Chocobo you can get. It can also cross any terrain on the map, including water.
Another way to get a Golden Chocobo that I just discovered is to get the Desert Rose, the reward from the Ruby Weapon, to the Kalm Traveler. Depending on your group and skills, this way could be less painful.