If you walk into a shop, and you see three items on the shelf, you're far more likely to buy one of the items on the shelf, than the one that's hidden behind the counter that you have to ask for.

It's not force, but almost nobody will ask for the thing behind the counter. It's the effect that matters.

Up to a specific level, yes. A simple example of that is the loss of reasoning upon a lifethreatening situation.

The extent of the grey area differs for each individual.