Are long form personal pronouns always required after prepositions - so as here αυτόν, not just τον?
That is correct!
Why μετά without από is wrong?
I guess because you are requested to translate "after HIM" and υπογράφουμε μετά simply means "we sign after(wards)".
Hi, GP - My understanding of Bruno's question was "Couldn't it also be 'μετά αυτόν,' without the 'από' between them?" (This is a question I also had.)
the same 2 prepositions?
Why απ' αυτόν is considered a typo? Isn't that correct με τον απόστροφο?
I think it is correct. Many words are shortened with an apostroph in Greek.
Yes, it has been added.
Is μετά από used as a preposition of time in this example?
It indicates position/time. Same thing in this exercise.