I have smarthub refrigerator with demo firmware

can help me to get stock firmware tizen 3.0

This forum was set up a couple of years before Samsung acquired smartthings and is for customers to help other customers with the Home Automation system.

If you’re looking for help with Samsung brand appliances, vacuums, or televisions, including how they work with the “SmartThings (Samsung Connect)” app, see the official support forum, which includes assistance from Samsung staff:

https://us.community.samsung.com/t5/Get-Help/ct-p/get-help

So in your case that’s the best place to start.