Hello MS_7,
Welcome to Microsoft Community.
In your description, I notice that you seem to have the option to log in with a password, but after a while you will be prompted that you cannot initialize Microsoft.net Framework 4.0 or later.
Can you clarify here whether you are free to operate your Surface before or after the prompt?
Assuming that you can still operate normally, then this means that you at least have the conditions to back up data, please backup all important data as much as possible.
Then, try to reset the Pin at this point. Click on the Start menu -- Settings -- Account -- Login options --Pin (Windows Hello), try removing the login option here, and then reconfigure it.
However, my best recommendation is to create a local administrator account immediately to prevent the situation of completely no account available:
Manage user accounts in Windows - Microsoft Support ****
However, if you cannot perform any of the above operations, it means that neither you nor I can perform any operations on this device at this time. The only solution is to create a Surface-specific recovery drive and use it to restore your Surface Laptop 4 to factory condition. The full explanation is in the video linked below:
Creating and using a USB recovery drive for Surface - Microsoft Support ****
Since the current Surface Laptop 4 doesn't work, you'll need to create a recovery drive using another Windows device.
Best Regards,
Mitchell | Microsoft Community Support Specialist