How long until an inactive Instagram account becomes available?

[Cat]

I am unsure of specific Instagram policies but I do know that that "Accounts may be permanently removed due to prolonged inactivity" (according to the official site). When an account is deleted, does it become available for another user to register as? And how long can an account remain inactive for? The username I would ideally like has not been used in over two years.
Thanks!

[Giasho]

I thinks you have to give valid reason for delete your account... if it is valid it cannot be deleted