qadha salaah

Qadha namaaz

Q: If anyone starts to offer 5 times namaz at any time of his life, so is it mandatory for him to offer all the due salats (Qaza-e-umri) first, which he has not been prayed since he was 12 years old?

Qadha of Esha Salaah if a woman's period ends before fajr

Q:

1. A woman is on her period. She goes to sleep at night but when she wakes up at fajr time, she realises that she must have become taahir during the night since there is no trace of blood. Does she have to make qadaa of the isha prayers? 

2. Would it have been necessary for her to set her alarm clock to wake her up before the end of isha time/start of fajr time, to check whether the period had finished at night, in which case she would avoid it becoming qada?

Omitting Salaah in college

Q: I usually get dropped off to college around 9AM and by the time I get picked up from college, the time for zuhr and asr prayer are already passed. Is it sinful for me to not be praying those salah? Is it okay for me to make up for the missed salah by praying the optional rakats of Maghrib and Isha?