Salaah

Q: My local imam makes some mistakes sometimes in salaah and I need to know whether these mistakes invalidate the prayer.

Mistake 1) The imam sometimes says hamza/alif Instead of saying ein for reciting quran, does this invalidate the prayer?

Mistake 2) For the name of Allah, Al-Quddus in the quran, the imam changes the seen into a saad-does this invalidate the prayer?

Q: Can we offer namaz behind a person who commits shirk or has the aqeedha of shirk?

Q: In Deoband the Ulama say witr prayer in Kaaba is not valid and we need to repeat it as it remains due. Is this correct? Also, can one pray 1 or 3 or 5 rakats in witr?

Q: If the ahle hadith wash their feet with water during wuzu after taking their socks off can we offer salah behind them?

Q: Is there any Saheeh daleel that Rasulullah (Salallahu Alihi Waslam) and the Sahaba (Radiyallahu Anhum) prayed eight rakat taraweeh? Is taraweeh and tahajjud different salat to be prayed in one night?

Q:

1. I went to sujood. My finger was on something, so before reciting anything I flicked it away and put palm flat and carried on.
2. In third rak'ah I rose from sujood and like in the position where you support yourself to get up I moved my left foot flat and realised its not sitting before getting into it and moved my foot back upwards and supported myself up like about 10 seconds from sujood takbir to the basmalah of 4 rak'ah.
3. Disc solid small spot, not paint, perhaps likely a eye secretion under my eyelid at about 6:30, I made Wudoo' at about 5 to 4 (3:55) and was done with Fajr at perhaps 5:15. (I was awake for Dhuhr all way to &past fajr), should I disregard it as having come later and ignore it?

Q: Sometimes in rukoo' I do the thikr and then I straighten myself a bit and hear a crack, so does that mean my back only became straight when it cracked? If so do I do the thikr again? Must the back in sujood rukoo sitting and standing always be straight or at ease straight? Is the neck or head considered in this?

Q: Majority of the time when I do sujood, my little toe doesn't touch the ground and perhaps the two besides it, but the big toe and one next to it  mostly do if not all do, so, is all toes touching the ground with pressure waajib/Fard, if so should one make movements in sujood or seating to ensure they touch the ground? Also I am not able to remember all the times this has happened, a lot though.

Q: What is the ruling on reciting inaudibly, is there a consensus on its permissibility? Like without noise and just moving the tongue.

Q: I usually read my witr salaah at the time of tahajjud, after the tahajjud salaah. However, sometimes by the time I finish my witr the fajr time has set in. Will this be regarded as qadha? Will I have to repeat it? Will it be better for me to read the witr before sleeping?