Is the 2% fee, taken once when the first installment of a loan is paid – after it was a bank interest and then canceled and considered an administrative fee – considered usurious interest or not?

Usurious interest on a loan is forbidden. As for taking actual administrative fees, there is no harm in it, provided that it is a pre-determined fee, and it is not permissible for it to be a percentage linked to the loan, because that would make it interest, not a fee. What matters are the realities, not the words. And taking usurious interest even once does not make it cease to be usury.