Is it permissible for someone who intends to make up the Asr prayer to lead someone who is praying Maghrib, and in the event of leading, should he recite aloud or silently, and what is the position of the congregants then?

It is permissible to pray Maghrib behind someone who is praying 'Asr as a missed prayer (qada'). In this case, the congregant (ma'mum) sits after three rak'ahs and does not follow the imam for the fourth. It is preferable for the congregant to wait for the imam to finish and then make the taslim with him. It is also permissible for the congregant to separate from the imam and make the taslim independently. The imam does not recite aloud in this 'Asr prayer, and this does not affect the congregant's prayer, as silent recitation is desirable in its place and the prayer is not invalidated by its omission. The imam bears this for the congregant.