Does the Takbir upon going down for prostration end upon reaching the ground or upon prostrating? And is it permissible to complete the saying of "Sami' Allahu liman Hamidah" after straightening up from bowing?

The Takbir for prostration begins with the descent and ends upon reaching the ground. As for completing "Sami' Allahu liman hamidah" (Allah hears those who praise Him) during the rising from bowing, there is no harm in it.