Please help me!!!!!! 1. Can I beat ansem at lvl 52 at final rest?

Yes, you can beat Ansem at level 52, but it's near impossible. The best two places to level up is (suprisingly) Traverse Town and the Hades cup in the colliseum.

The hades cup is hard to beat unless your lvl 60 or higher.

You should beat the hades cup alone and in the time limit match after you beat it the first time to get donald and goofy's best weapons. Finally.

Yes you can return to the final rest save point. (You should beat the angel heartless to get orachilon to forge Sora's Ultima Weapon)

Yes you could and this is how,
You know Ansem transforms like 5 times, well first you should always have aero on and have items for magic. Cure constantly even if you are half down do it any way he is powerful. Oh and when you do beat him watch the credits because at the end they have a short cut scene then after that the K.H. game cover shows up and you have to turn off your PS2. Because thats the end of part one you have to wait for kingdom hearts two. Finding all the trinities is hard but I can't tell you where they all are. And to see the seceret movie you have to get all puppies, post cards, and trinities.