Dua during salat and congregational prayer question

Assalamu Alaikum

1. Can we say dua in prostration and when sitting after tashahuud? Sunnis say it is the best time to make dua, is this true in the madhab of the Ahl Al Bayt?
2. Do we move at the exact same time the imam moves or is it slightly delayed? When we say salam at the end, how much after the imam says the first salam do we start saying salam? 

Wa Alaikum Salam, 

1.  Imam Murtaza Muhammad bin Yahya al Hadi, peace be upon him, stated that this is not allowed. 
2. It is slightly delayed, The Tasleem is to be given after the Imam has given the Salam towards right and left

 - You may Refer to this video for the manner of the congregation prayer.