Sajda-e-Sahw

Q: I mistakenly stood up after the last sajdah of the last rakaat of salaah. How should I proceed with the salaah to make it valid?

Q: If while praying two rakaats salaah, after sujood of the two rakaats, one forgets he has completed one or two rakaats and therefore stands up with the intention of praying one more rakaat and doing sajda sahaw but on standing he remembers accuratley that he in fact has completed two rakaats.

1. In this situation, while he has stood up with or has already started reciting Surah Fatiha, is it permissible to go to tashahhud or one should complete four rakaats?

2. Would sajdah sahaw be needed after completing four rakkats?

3. Or salah will not be valid and one must repeat it, if for example he was praying two rakaat sunnat muakkadah of Fajr or two rakaats Fardh of Fajr because he has prayed four rakkats instead of two?

Q: I was reciting Surah Faatihah in place of Attahiyyaat. I realized at the time when I was going to lift my index finger. I stopped Surah Faatihah then recited Attahiyyaat and ending with sajdah sahw or I completed Surah Faatihah and ending with Salaam only. Will my salaah be valid? If not, kindly inform me as how do I correct such an error in salaah?

Q: I took a moment to try to swallow something which I felt was going to come out my throat during salah. But I didn't swallow - I ended up burping/belching. The time this took I think exeeded three Subhanallahs. Is my salah valid?

Q:

1. In our college, the student imam, in between 2 sajdas forgetfully said, "SamiAllah huliman Hamida" instead of "Allahu Akbar", he did a 2-3 second pause and went for the second remaining sajda. The people behind him didn't even correct him but the second row guys had to correct him, by saying "Subhan Allah". After the completion of Salah, there was a big argument,

a. 3-4 people did sajda sahu after salah

b. The rest of the guys said "the Salah has to be repeated because the imam's niyyat is muqtadi's niyyat and if he makes mistake, it affects everybodys salah"

After that, the whole Salah was repeated by a different imaan. Who was right? a or b?

2. The imaam got up from ruku, and said "Allahu Akbar" instead of "SamiAllah huliman Hamida". The people behind him didn't correct him. The second row guys corrected him the wrong way, but this time by saying "SamiAllah huliman Hamida" instead of "Subhan Allah" and at the end, the imaam didn't even make sajda sahu. I have to repeat the Salah right? Because I have heard the imaam's niyyat is the muqtadi's niyyat and if he makes a mistake, it affects everybodys salah.

Q: How many different ways can one perform sajdah sahw? I like to do 2 sujood and say salam after finishing whole namaz in normal way. Is this right?

Q: During a four rakat prayer, if one has forgotten whether they are in rakat two or three, and they decide two is more likely so they sit and read attahiyyat, do they also have to read tahiyyat after the next rakat, which they assume is the third one?

If one is not sure whether they are in rakat one or two, and they decide two is more likely so they sit and read attahiyyat, do they also have to read attahiyyat after the next rakat?

Q: If I forgot to sit in tashahud in the last rakaat of Asr Salah and stood up, what should I do now? 

Q: After every single namaaz can I do sajdah twice then make salaam and count it as sajdah sahw. I feel like my namaz isn't perfect that's why I do short sajdah sahw after every namaz.

Q: In almost every salah I tend to think that I skipped something that I need to do sajda sahw for, but I believe it is not correct everytime. No matter how much I tend to focus and not do sajda sahw, I think that I skipped this out or that. What is the ruling in such a case?