Those things which render the Salaah invalid

Switching off the phone during Salaah

Q: I know if a person's phone rings on loud during salaah, it is permissible to use one hand and switch the ringer off. If the phone rang very loud, and the person expects that it will ring again, someone mentioned that it will be permissible with one hand to take the phone slightly out the pocket, and look at the screen and press a couple things to switch it off (because today's phones can't be switched off without looking). Is this permissible?

Moving back in Salaah

Q: Two people are praying, with the muqtadi praying to the right of the imam. A third person then joins and pulls the muqtadi back to stand with him in a row behind the imam. When the muqtadi is pulled back, he ends up taking more than three steps due to the surprise factor (he takes about four small steps). Will this break his salaah?

Making sounds in Salaah

Q: While reading namaaz different types of sounds come out like when I close my lips and while opening the lips and due to the movement of the tongue some sound is generated and while reading rabbana lakal hamd near hamd different sounds comes out, when the tongue touches the upper lip. Do this kind of sounds invalidate my salaah? Can you tell me which kinds of sounds invalidate salaah and which of them don't?

Turning in Salaah

Q:

1) In salaah, if you move your head in any direction (right, left, up, down, back or forth), does this nullify the salaah?

2) Moving your chest in salaat in a direction away from the qiblah, does this nullify salaah?

3) If your pants has a small hole and your skin is visible through the hole, performing salaah in this state, will your salaah be valid?

4) If the underneath of a shoe touches the top of your feet, do you have to wash that part of your feet before performing salaah?