It sure as hell wasn't an "ex-colony," whatever the hell that means.
No it was a territory. It became a state when Congress voted to admit it. The other states, in effect, created the state of Alabama and every state after the the original 13. If approval of the other states is required for a state to come into existence in the first place then why should it be so hard to accept that the approval of the other states should be required for a state to be removed?