Witr and Nawaafil

Q: Can a person read any nafl or qaada when tahajud time end before the fajr azaan.

Q: My question relates to the times of Tahajud. When i was in madressah I was taught that we could read from just after 12am till about 15min before fajar salah. Recently I was told many different things regarding the times. What would be the right time to read Tahajud salah and the cut off time?

Q: I would like to know if it is permissible to recite Salaatul Istikhara even if you only intend on marrying the desired person after a couple of years. I have heard that after reading the Salaah then nikaah should not be delayed. Please can you also tell me more about the Salaatul Istikhara that is read on a persons behalf, also what are the conditions of that Salaah?

Q: An Imaam performed twenty rakaats Taraaweeh during the month of Ramadhaan. This Imaam stood up for the third rakaat without performing tashahhud. He completed the salaah by performing four rakaats. Is the Taraaweeh salaah valid if performed in sets of four or six rakaats?

Q: If the person performing the taraweeh misses the Esha Salaah with the Jammat, is he still allowed to perform the taraweeh?

Q: Are there any specific virtues for performing salaat-ud-duha and how do you calculate its time?

 Q: Is there qadha for taraaweeh salaah once the time passes?