Not even dual boot.
Just depending on the password/pattern entered, log in as a different user. It's possible to do in Android as an app. I've been meaning to write one, but it seems like lots of work and upkeep.
What you describe might be almost achievable using Android work mode, and an open source tool like Island - you can have a second instance of apps (like WhatsApp or signal or telegram) independent of the first instance, and you can turn work mode off if needed.
If your adversary knows about work mode though and checks if it's available, this won't help you much.
