[Samiun]

, can I pray salat tahiyatuul masjeed after or before the imam azan then salat qabliyyatan jumaah'? Is it necessary to stand and not perform prayer or sit down when one hears the adhan? What is the dua for when the khatib recite at the end of his Khutbah causing every1 to raise their hands up n then say 'ameen' after certain duas?