Yes, and it may be a good idea to have it just in case. But the courts in the US so far mostly ruled that police forcing you to give biometrics to unlock is fine, as it is the same as fingerprinting you when you are arrested. But forcing you to give pin/password is the same as testifying against yourself, which is against the 5th amendment. So they usually can’t make you to give them a pin/password. At least in theory. Still better to have it in practice.
Graphene even has an option to enter a fake pin and wipe the phone iirc.
Yes, known as Duress password.
Yes, and it may be a good idea to have it just in case. But the courts in the US so far mostly ruled that police forcing you to give biometrics to unlock is fine, as it is the same as fingerprinting you when you are arrested. But forcing you to give pin/password is the same as testifying against yourself, which is against the 5th amendment. So they usually can’t make you to give them a pin/password. At least in theory. Still better to have it in practice.