2020 450ho says it's overheating but
 

450 says 100c only after 3-5 minutes, the coolant isn't even warm, atleast at the radiator cap, so I am guessing it is either a bad sensor or bad thermostat..Which is a more common problem, only use it for short trips in a open field seversl times a month, so I was thinking of bypassing it or the thermostat but I can\t find either one.

450
 

What year? It makes a difference. Could possibly be the thermistor in the radiator. Could be a bad thermostat. That’s located on the engine. Could be the impeller on the pump is bad or broken. Do you have flow in the radiator? Do both hoses get hot?
You need to check these things before you throw the parts cannon at it.

check to see if all the hoses are evenly hot. if not, then maybe thermostat. I'm assuming there is not an air bubble which usually only happens if you have drained the system.