I wondering to know during time of another Imam after Imam Hussein as, when they pledge allegiance to Imam Jaafar (AS) for example or Imam after him, do they still join the pray or any ibadah or hold to any fatwa of other than Shia community meaning fatwa which is of their Imam for them not from AhlulBayt lineage?

It is known that Muslims used to pray together, and the disputes were not many according to the apparent, and the mosques were furnished with sand and stones, so the problem of prostrating on carpets did not exist.