Conditions for the validity of Salaah

Q: Can we delay isha after midnight? If not, what is the last time to pray isha?

Q: I prayed salah from puberty with proper wudhu but without ghusl for 7 years because I was not aware of the masalah of ghusl. Should I reperform those salahs?

Q: Can a woman only where a scarf whilst performing salaah? The hair is exposed in front?

Q: Is my salah in nike clothes valid?

Q: A woman wears a long dress and a burka while praying Salah. She is however, not wearing a trouser (her dress is long that covers her legs). Is this ok or does she have to wear a trousers also?

Q: After praying Fajr, can we offer nafl or do we have to wait after sunrise?

Q: As the Asr prayer for the Ahnaaf starts after Mithle-Thaani, in Gulf countries it starts at Mithle-Awwal and the jamaat of Asr in the Masjid is made whilst the Dhuhr time of Ahnaaf is still going on and since in each and every part of the Gulf the asr jamaat is at earlier times, what should a person do? Should he join the jamaat or should he pray alone for Asr prayer? 

Q: How many minutes after sunrise can one pray again? Is it correct that one cannot pray salah as well as quran during sunrise or only salah (qadha)?

Q: Can a person read Salaah with a Topee only and no Kurta?

Q: How many minutes before sunset is it not permissible to make salaah or sajdah-e-tilaawat? Some say atleast half an hour before sunset and some say about three minutes before sunset.