They can run in within 30 mins of accepting that mission. So if they accept it at 8.59, the latest they can run it is at 9.29 (which is 29 mins past the event's close time).
Its not as if they can just run it any time like at 12 midnight or something. It still has to be within the 30 mins windows as like all other Convoy missions.
Absolutely.
Convoy still has to be accepted within the required timeframe.
Anyway, thread has been answered with additional information. Hope that clears it up!