Copyright of songs made by you

The question is, who owns the copyright in the free version? If you use the platform as a tool to improve a song you registered and published years ago (i.e., it's your own work), and you only want to create a remastered version (for example, if you tell the AI ​​you want your song to have a specific style, respecting all the melodies of the original and adding your own lyrics), are you the copyright owner? Can you register it since it's a derivative work of an original song? Do you have to pay for the certificate in the paid version?

Dear Tunee Ai,

Its been fun to create music with you. I have some querries if you can answer for that but initially try to understand my problem…..

I started producing a content for youtube… its a sci-fi character ainoo badshah… its a character of superhero girl . the ultimate objective is to make kids understand everyday science using, rhymes, music, and ofcourse episodes.

But

  1. I used your free plan, please let me know as i was not aware of the this before
  2. Will youtube accept my music for free plans regarding monotization.
  3. if the channel is monotized and i have no copyrights of music. will tunee ai get paid by youtube or my channel as i have no copyrights.
  4. i am ready to buy a paid plan for music generation to get music certification of copy rights but what i have vreated so far… will i be able to get copyrights of thouse already created songs.. if yes then how… me and my team used multiple emails to create diffrent songs. but its a total of 6-8 songs… that needed to be copyrighted… kindly tell me how to do that.. and if tunee ai,. kindly reply me..