Your drain is plugged
I found a link that says it should be under the evap coil in the back. I will pull that panel off and see if it is frozen over.
That ice on the evaporator is not from a clog drain in the picture you first posted.Are your door gasket OK?Is the dispenser flap closing?Are all the fan motors working,fan in freezer and fan by compressor working.And does it have that ice on the evaporator again like in the first post or is it just the drain.
Pour water on your evap coil with the cover off and see what it does