In order to prove that the angles RST and TUR are congruent, the lines 1, 2 and 3 of statements and reasons are correct.
Since triangles RST and TUR have all three sides congruent, so they are congruent triangles by case SSS.
For the line 4, the statement is "angle RST congruent to angle TUR" (what we want to prove), and the reason is "corresponding angles of congruent triangles".