According to Zaidi fiqh, saying the salaam to the right and left is obligatory. It is narrated in the Majmu' of Imam Zayd that Ali used to say salaams to the right and left.
It is narrated in the Amali of Ahmed bin Isa that Abu Razin (in some reports, Abu Zayd) said:
"I prayed behind Ali (as) and he said the salaams to the right and left: As salaamu alaykum wa rahmatullah. As salaamu alaykum wa rahmatullah."
In his commentary on At-Tahriir (a book of Zaydi fiqh), Qadi Zayd said:
"Imam Nasr (as) said in his Al-Kabiir: 'All the Descendants of Allah's Messenger, peace and blessings be upon him and his progeny, hold to the view that two salaams should be said to the right and left if in congregation. When they are lone they also say the salaams to the right and left..."
This does not take one away from facing the qibla because it is ones chest and front portion of the body that faces the qibla. Even if one turns his head, he is still facing the qibla.
Regarding prostrating on natural materials, like earth, grass, reed mats, etc., it is considered praiseworthy but not obligatory.
And Allah knows best!
