Minimum duration of postures in salaah
Q:
1. What is the minimum duration for sujood, qaumah and ruku without which salah will be invalid?
2. If one says Subhana Rabbiyal Azeem and Subhana Rabbiyal Aala once only due to time constraints and if leading salah says Sami Allahu liman Hamidah and goes to sujood, would it suffice for salah to be valid or one has to wait for muqtadees to say Rabbana lakal Hamd?
3. If while leading salah, and in ruku the imam feels by the sounds of steps or running to catch the rakat, is it permisible for the imam to prolong ruku to allow them to catch the rakat?