ANSWER:

Gathering in homes for mourning is an innovation. 

When someone dies, people visit their homes for 3 days and make duas collectively. Is this allowed? If you can please give me the reference too..

Funerals | December 31, 2017 2:54 pm
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One boy asked me that may be his mother’s father died in USA and his kabr or grave was given by placing his body in a box.I mean that the body was in box and then the box was buried.So my question is that is it permitted or haram if haram then what should they do because he is now buried.
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Is the relation of a wife and husband terminated with the death of either of them ? If in affirmative, in what words one should pray for the departed soul ?