1. Probably brushed the ball more than you think - with inverted you wont get any passive reversal against incoming top spin. So you would need to brush finer and harder to get this extra heavy back spin.
2. Whenever they want!
3. Depends how well the chop is disguised. A super chop is not too difficult to return, provided they know bbn it has mega spin on it. There is always some noticeable difference to create a heavy spun ball vs a dead or lighter spun ball. Your strokes literally cannot be identical and have different spins.
Check out this video
https://youtu.be/sJsokqn2Nw8