Is there a reason for 乞う to conjugate to 乞うて?


Usually, when conjugating Godan verbs ending with う into て-form, you would get
って instead. Is there an etymological reason for this exception for 乞うて? I saw
this in a rather recent book written in the last ten years, so would the
modern Japanese progressive form of 乞う be 乞うている?

I've also read that some other verbs also use this conjugation, but it sounds
rather archaic. For example, 問う→問うて、沿う→沿うて. Are there other verbs that
conjugate this way in modern Japanese?

