7) Based on my credit agreement may I ask when is a VISA closed?
The rules about closing credit card accounts are complicated and peopel often complain about being hit for charges later.
8) Am I liable for this charge?
Yes, I would think so. Calculating interest is complicated and it's not always easy to finalise an account on a particular day.
From your description of it, you have a very good relationship with AIB. They gave you a term loan to clear your credit card and for education fees.
This relationship is very valuable. Don't lose the head. But enquire about it and ask them to waive the charge.
Brendan