Reason 2, where the [1] is at, is Definition of Midpoint
P is the midpoint of TQ and RS, so it cuts those segment into two congruent halves
Statement 3, where the [2] is at, is Angle TPR = Angle QPS
These two angles are vertical angles. They are opposite one another formed by the intersection of TQ and QS. Vertical angles are congruent.
Reason 4, where the [3] is at, is SAS Congruence Theorem
The two pairs of S terms are taken care of by statement 2. The middle angles A are the result from statement 3.