(1) Can I perform qasr after leaving my house immediately?
(2) While returning back from journey, I perform qasr at one place from which the distance up to my house is exactly 75 kms. Can I perform qasr?
(3) Can I pray full salah in journey or this salah is valid or not or I have to perform only qasr?
بسم الله الرحمن الرحيم
(1) If you intend to travel the distance of 170 kms then qasr shall be wajib on you as soon as you leave the border of your village.
(2) While returning from your journey until you do not enter in the boundary of your village you will keep on doing qasr.
(3) It is wajib to do qasr in journey and it is makrooh to offer full salah. If someone offered full salah instead of qasr and he did qadah on two rakah then his salah was complete but it is not good to do so.
Allah knows Best!
Darul Uloom Deoband
This answer was collected from the official ifta website of Darul Uloom Deoband in India.