Subtle distinction: I don't think the police, even with a warrant, can force you to open anything. They can use force to open something if you refuse (or seemingly, if they feel like it), but they can't make you do it.
A court on the other hand, can compel you to open something.
Yes, but that is a court order issued by the court not the police.
An order to unlock something coming from the cops is entirely different, even if they have a warrant. Warrants would allow them to seize a phone, but you don’t have to provide the password.
A court on the other hand, can compel you to open something.