بسم الله الرحمن الرحيم
(1) You should start qasr after you leave the boundary of the city or village where you live.
(2) If the place which is located on the distance of 15 kms is out of your city, then you would offer Zuhr as qasr there.
(3) It also carries the same ruling as question no 2.
Allah knows Best!
Darul Uloom Deoband