Problems with Frigidaire FRT18HB5DW0 Top Freezer Refrigerator

There is something plugging the drain line in the freezer which carries water from the defrost cycle to your evap drain tray in the bottom of your fridge. The water has built up and froze plugging the flow of air from freezer to fridge.... find the line and unplug it and let fridge sit and thaw overnight and then some more.

if you can; find the vent(s) between the top and, bottom boxes (where the evaporator fan is located: closing these vents makes the freezer colder and, the refrigerator warmer, opening these vents the reverse is true.

The baffle that opens to allow cooling into the refrigerator may be blocked, broken or mis wired. These units work by just cooling the freezer and then blowing some cold air into the refrigerator whenever the fridge thermostat calls for it. The fridge's thermostat is trying to cool the refrigerator but something is preventing the cool air from getting to the refrigeration part, that's why it's freezing up the freezer

check to see if fan inside freezer is running.
is the evap coil in freezer froze up ?
if fan is running and coil is froze up u need a defrost timer.

check to see if fan inside freezer is running.
is the evap coil in freezer froze up ?
if fan is running and coil is froze up u need a defrost timer.

check to see if fan inside freezer is running.
is the evap coil in freezer froze up ?
if fan is running and coil is froze up u need a defrost timer.

i suspect the fan is not working. take the back panel off inside the freezer and check that the fan is free to rotate, check for continuity thro the fan motor and check you have power to the fan

you are right about the cause of water in the fridge - blockage in the drain. i'v never met this caused by ice but it is possible.
with the freezer, the cause of the fault is the fan not working - probably jammed with ice. take back panel off inside freezer and check for ice build up. if loads of ice thgen defrost system has failed. you can do a temporary repair by melting the ice off with a hairdryer

Make sure your fan is working ,its in the freezer behind panel .If not the fan your passage area is probably covered with ice and the air cant get in freezer

the unit is loosing the freon supply to the evaporator.you either have a leakage,a blockage or the compressor is not pumping to full capacity.