Freezer goes off for too long every couple days and stuff starts to melt before it comes back on and starts freezing again frididaire model frs26kr4dq8 mfg 07-05

Sounds like a defrost cycle problem. This is one of many good videos that help with troubleshooting refer/freezer problems.
Defrost Thermostat Replacement (part #W10225581) - Whirlpool Refrigerator Repair - YouTube (http://www.youtube.com/watch?v=U950xyscTMg)

Here are some manuals: https://dl.dropboxusercontent.com/u/8010163/Frigidaire%20Refrigerators.zip
You may need a defrost timer or if it is electronic it could be something like a thermistor. You will have to test the parts.