muqtadi

What should the imaam and muqtadi say when coming up from ruku?

Q:

1. Do you have to read samiallahu liman hamidah whilst getting up from rukoo or can you say it after you stand up?

2. Will the salah be invalid or makruh if one says it after getting up?

3. When praying salah in jamat, when the imam says samiallahu liman hamidah does the muqtadi have to say it too or can he just say rabbana lakal hamd?

4. Likewise, does the imam have to say rabbana lakal hamd or does he just say samiallahu liman hamidah and stays quiet after that?

Muqtadis reciting Surah Faatihah in salaah

Q: In chapter no 7 (Surah Al-Araf) verse number 204 it is stated that "When the Qur'an is read, listen to it with attention, and hold your peace: that ye may receive Mercy". So why do people when praying Fajr, Maghrib and Isha (fardh) behind the imam (first 2 rakahs), when the imam finishes reciting surah AL-Fatiha, many people recite surah fatiha, although the imam is reciting another surah. Please do clarify this.

Muqtadi's head touching the mimbar in Salaah

Q: Because of the Musjid being overcrowded and the mimbar being an obstruction in the first saff of the Musjid, a muqtadi happened to stand in the first saff directly in front of the mimbar, and when he (muqtadi) went into sajdah, his head touched the first step of the mimbar (he basically made the sajdahs with his head touching the first step of the mimbar). In the above mentioned case, was his (muqtadi's) salaah valid since he carried out his sajdahs in this manner?