I heard that duas cannot be asked in group and it should be asked alone but In my country, after every prayer , after completing the dhikr , imam asks Dua and all people say ameen thinking that the Dua imam is asking will be accepted for them . So is the imam doing right and duas will be accepted or is it wrong ?
Every innovation in the Deen will not be accepted, and you should not say Ameen to that duas. saying Ameen to what he is saying is like you are accepting what he is doing.
'Aishah (May Allah be pleased with her) reported: Messenger of Allah (ﷺ) said, "If anyone introduces in our matter something which does not belong to it, will be rejected".
[Al-Bukhari and Muslim].
The narration in Muslim says: "If anybody introduces a practice which is not authenticated by me, it is to be rejected".