Those things which render the Salaah invalid

Q: If a person applies Vaseline in his nose and thereafter begins his Salaah. During Salaah he sniffs and the Vaseline goes down his throat. What is the condition of his Salaah?

Q: Five minutes after salaah, when I go to the toilet, some times I observe that a drop of urine is evident on the tissue between the underwear. Now I want to ask that after all the precautions you mention, if I notice such a thing, would my namaaz be valid?

Q: If a person is holding a handkerchief in his hand and performing salaah due to his nose running, his postures in salaah will be slightly changed, e.g. in sajdah he will hold his hand sideways or upside down so the hanky doesn't touch the floor, and in qadah his hand will be slightly lifted off his thigh with the hanky in between. Is it permissible to do so? What other options are there?

Q: If a person is performing salaah and needs to check the time so as not to miss Takbir-e-oola.

1) Can he look at his wrist watch which may involve him having to move his kurtha and tilt his wrist in qiyaam?

2) If it is dark would it be permissible to press the light button with the other hand as well?

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?

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?

Q: While reading salah saying Allahu akba will that break my salaah? Suppose I'm going to ruku if I say Allahu akba and to correct it can I again say allahu Akbar when I'm in ruku or doing this will break my salaah?

Q: If we control gas during namaaz, will it be valid or not or again we need to perform the prayer and wudhu? If we are not sure that wind is passed or not at that time, then what should we do?

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?

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?