I want to ask if qasr is applicable to me, then also if I offer 4 rakahs fardh for Zuhr and Asr in respective times instead of 2 rakah qasr then salah is valid or one must offer qasr only?
According to Ahnaf it is wajib for musafir (traveller) to do qasr. If he offered full salah knowingly he shall be sinful and it shall be wajib to re-offer that salah. And if he offered four rakah unknowingly then salah shall be valid after performing sajdah sahv.
Allah (Subhana Wa Ta’ala) knows Best
Darul Uloom Deoband