Has a pope ever resigned?
Yes, at least 11 popes have resigned for one reason or another
over the centuries.
It is not a question of a Pope being "allowed" to resign. The Holy Father is the Vicar of Christ on earth, he is subject to revelation and dogma, which cannot be changed, but that is all. Everything else, as long as he is Pope, he holds the final word. No pope has resigned for six hundred years, and in that case (Pope Gregory XII) it was a case of clearing up confusion about who…