Car overheating when driving and Hot air blowing cold

I was driving with AC on full blast when the AC went out and started over heating for first time.

I had a mechanic look at it and said it was clutch fan so I replaced it and it didn't work. Second mechanic said it was stuck thermostat so I went ahead and replaced it and still over heats.

No leaks that I can see, I have not pressure tested it yet. If anyone can please solve this mystery for me I will be very grateful.