ive got a 100% in the story and got all the vids and experienced the final episode howevr wat would happen if i delete it to lvl aqua up to make the final episode easier.

i don't know try and see what happens

Well you can train Aqua and then when it asks you if you want to make a new save file for the Final Episode, just put in a new save file of the Final Episode, and overwrite your old one.

I only beat the ventus story i just need terra aqua and the final epiosode to unloke the secret movie i heard its so sad

you could store the final episode you have now on your computer and try it out then when you have done it you can see if it works without deleting anything