purchasing instagram username

How is this possible? I bought @Chan instagram username from here a long time ago and got it banned 5 years ago... instagram told me it will be permanently banned. But how is it available now??? how do i find out who is selling this???

looking for someone who can get inactive accounts on instagram for us. the accounts in question are either very old or don't have any profile picture and have never been posted on in the past. if this sounds like something you can do or if you know of someone who can get it done please help!

How would you go about buying a username on Instagram if it would takes 2 weeks to claim the instagram name if the original owner is gonna give you the @? what if someone steals it before you can change it over to your username after the 2 weeks?