Rules question from Pack/Bears game re: replay challenge

[MicroBob]

Yeah, there should be zero incentive to say that you challenge the 'first down' if I'm understanding it correctly.

A challenge is supposed to mean that any other part of the play is included. You don't have to go through the list of things that you want challeneged to my knowledge.
All coaches know this.
Challenge one aspect and the whole play gets challenged.
So if you think he might have been out-of-bounds AND he might have trapped the ball you have to choose which part of the play should have made the pass incomplete and if you don't guess correctly then you are charged a time-out?
Weird and dumb.

What if they thought the guy stepped out of bounds just before reaching the end-zone....but the replay shows that his knee touched the ground back at the 50. The play is reversed and touchdown is overtunred and the ball is brought all the way back to the 50 but he actually didn't step out-of-bounds at the 2 so that team is 'penalized' and not allowed to use their challenge again?
That's just weird.

Incorrect phrasing or choosing the wrong part of the officials bothced-call/s when the challenge indeed does result in ANY ruling in your favor is stupid.