Drawing here:
https://www.phoenixfriction.com/Images/articles/hydraulics-diagram.jpg
Clutch master has a spring inside that will push pedal back up when your foot is off the pedal
If pedal doesn't come back up then either the valve in the Master is bad or the spring is, in either case its the Master that is the problem.
The slave doesn't have a valve or anything else inside it, it's just a cylinder that expands when fluid pressure is applied.
The Quick disconnect fitting on the end of the Master Cylinder's hose has a valve that is pushed open when slave connection is pushed into it
If Quick disconnect pops off or is not on all the way the clutch pedal can't be pushed down.
The Reservoir connection to the Master has a one-way valve, in the Master, so when you push down on the pedal the fluid is directed to the slave not back up into the reservoir.
As you release clutch pedal, and it comes up, if slave had a leak the lost fluid would be replaced from reservoir.
I would check that, if fluid does come up into the reservoir when pedal is pushed down, then again, master is at fault
Replacement Master should come with reservoir and hose to slave with quick disconnect fitting attached
And push rod attached as well
You should use a box wrench or socket on the bleeder to loosen it, not open end wrench or pliers, once it is loose you can use open end wrench for bleeding
And there should be a "nut" you need to hold while breaking loose the bleeder valve