Is delaying the Dhuhr prayer from 12:00 PM to 1:30 PM, and delaying the Asr prayer from 3:30 PM to 4:30 PM, considered performing the prayer outside its prescribed time? And when is a prayer considered to be performed outside its prescribed time?

Prayer times are determined by the legal signs, not by clock time. The time for Dhuhr begins when the sun declines from its zenith and ends when the shadow of an object becomes equal to its height. At that point, the time for Asr begins and extends until just before the sun turns yellow (an optional time). Then, the necessary time for Asr begins and lasts until sunset. It is permissible to delay the Dhuhr prayer after its time has entered and up to two hours before the Adhan of Asr, and similarly for the Asr prayer before the sun turns yellow. There is no harm in this, even though performing the prayer at the beginning of its time is better.