(Theoretically cuz i dont have enough tc) Could i change My username to Eymeil even tho its already taken by my alt ;-; am i able to change mah username?

If your alt is inactive for 3 years or if you would also purchase a namechange for your alt.

Otherwise no.

Does your alt need to be inactive 3 years even if you can verify that it's your account (providing you have the 100,000 TC required to propose a name change?)

oh ok thanks

Yes or you could pay 100k to change your alt name to something else and then pay another 100k to change your main account to the name you want