Please do a search on google for STC1000 manual . you will find videos and written instructions.
F3 is the compressor delay - stops the fridge from turning on again until a set time from when it turned off. You set this time, at least 3 minutes and preferably longer.
You have not set up the STC1000 correctly if you have your fridges switching on and off too quickly.
There will be no difference using a PID controller.
You need to set a fridge delay to stop this happening.
I have used STC1000 controllers on fridges for 10 years or so.
Use real apples and juice them or next best store bought juice.
Those kits use apple concentrate giving you little chance of getting real apple flavour.
Best cider I have ever made used fresh cider apple juice from somebody at Bathurst