Conditions for the validity of Salaah

Q: Can we pray Zuhr half an hour before Asr?

Q: Zaid prayed Zuhr Salaah in Asr misl-e-awwal time. Thereafter on the same day zaid prayed Asr Salaah in misl-e-awwal time. Is the Asr Salah valid? In the above situation if the Asr Salaah is not valid, does Zaid have make qadha of the Asar Salah?

Q: Is salaah acceptable if the trouser of a man is going very low from the back but the line between the buttocks is not visible?

Q: If a follower of hanafi fiqh prays asr salaah individually or as an Imam at a time when the time of asr has not started according to the hanafi maslak but started according to the maslak of the other three imams, is this salaah valid?

Q: Is topi (head covering) for men is necessary in salaah?

Q: What is the end time of the (a) Israaq prayer and (b) Duha prayer? I already know their start times and preferred times, but would like to know their end times please.

Q: I want to know if a man's trouser is minorly torn at different places, can he perform prayers or do dua?

Q: I've prayed Salaah with a garment on many occassions and just recently discovered a hole in it slightly above the knees. Since the male awra is above the knees does that mean all of those prayers were invalid, and do I have to make them up? Also do skinny jeans invalidate salah since they show the shape of the legs?

Q: I heard that praying fajr after sunrise is an act of shirk. But what if I accidentally prayed fajr 2 minutes after sunrise without knowing it was past the time for fajr?

Q: Recently I performed two Salaahs at a jamaat khana. However the next day I realised my underwear was soiled. What should I do?