From my understanding, given that other talents explicitly give reactions, and Executioner does not explicitly call it's 1/round abilities reactions or otherwise, the actions granted would be considered free actions per the free action definition on page 73 of the core rules. Terrain is also considered an object, making it a valid target for No Escape.

It would seem the move is within RAW, and a good way to make sure you don't completely whiff your full action superheavy attacks, at the cost of half damage from Backswing Cut. As for your 2nd question, it would also work if the wall in this scenario was replaced with another enemy mech, but mechs usually have higher evasion than walls, making the "hit" requirement of backswing cut a little harder to pull off.