STA-BIL advertises gasoline integrity for 24 months
It seems you have exceeded the advertised lifetime of 24 months by 12.
Drain all fuel from the gas tank, fuel lines and fuel pump
Inspect inside of fuel tank for rust and/or varnish from evaporated fuel
You may need to clean your fuel injectors, you may not.
Clean various components with carburetor cleaner.
Reassemble and fill with completely fresh fuel
Is the gas beyond saving?
Yes, throw it out
Would it cause harm if I try to start it up?
Probably not but you could clog your fuel injectors if the gas is in bad shape and create more work for yourself than simply draining everything out and starting with completely fresh fuel.
STA-BIL has a product called "Start Your Engine" which gives back the combustibility of the gas.
Will this help?
It might. I wouldn't use it though. I would just drain out the 36 month old gas start fresh. You might have water accumulation in the bottom of the tank as well, as before, I would drain it.
Has anyone used this?
I have not, I typically don't use these types of products. I prefer to completely drain fuel systems for storage and start fresh so I don't have any experience.
You might want to try and simply drain the fuel system, add fresh gas and start the bike. I would also change the oil, filter and coolant as well. You might find that the bike just starts up. I would not use the old fuel or try and save it under any circumstances.