2020 iMac as a display for MacBook Pro

Once the first 27" 5K Retina iMac came out in Late 2014, Target Display Mode went away, never to be seen again. So your 24" M1 iMac doesn't have it. Apple also added restrictions on Target Display Mode after the fact so that even if you had an old iMac that supported TDM, the 14" M2 Pro MacBook Pro would be "too new" to use it.

Use your iMac as a display with target display mode - Apple Support

You might try using AirPlay to Mac. If you are running Monterey (or later) on both of those Macs, they would appear to meet the system requirements for this feature. In this case, you would set up the iMac to be an AirPlay Receiver, and then AirPlay from the MBP to it (as though it were an Apple TV set-top box).

macOS - Continuity - Apple

System requirements for Continuity features on Apple devices - Apple Support

Set up your Mac to be an AirPlay Receiver - Apple Support

This is not the same as a hardware video input, and it's possible you might see some lags. However, if it works, it would let you do what you want without the expense of a third-party product like Luna Display or Duet Display.

No, Macs are computers they are not displays for other devices.