1) Does one have to offer salah which was missed before a boy had his first ejaculation?
بِسْمِ اللهِ الرَّحْمنِ الرَّحِيْم
In the Name of Allah, the Most Gracious, the Most Merciful.
1) No, he does not. However, if his first ejaculation took place after the age of 15 lunar years, then he must do qada of any salat that he missed from the time he reached the age of 15 lunar years. (Shami: 6/153, Saeed)
2) One can do qada of the missed salats at any time during the day and night except at the following three times: 1) At the time of sunrise until the sun does not become so bright that one is unable to look at it for some time without difficulty; 2) When the sun reaches its zenith (i.e. zawal time. To be on the safe side, it is recommended that one does not offer any salat 5 minutes before and 5 minutes after zawal time); 3) Before sunset when the rays of the sun become weak until sunset.
3) He should offer qasr of the salats that he missed while travelling, even if he is currently in his hometown.
And Allah Ta'ala knows best
Mufti Faizal Riza