When my grandson locked a bedroom door from the outside, I looked everywhere on the internet to learn how to easily open it. Didn't find easy instructions but finally figured it out.

I assembled this tutorial to make it much easier to figure out than what I found. It's easy to pull the doorknob and it will be a snap to open the door when you can see the internals. Once you know how it lays out, you'll be able to open without removing know in the future. Two kinds of releases - this video shows a square plunger that must be pressed. The other kind will have a slot that can be rotated by a bladed screwdriver. Easy to figure out if you pull the doorknob (takes seconds when you know how).