The top radiator hose is hot water coming from the engine, it flows through the radiator which dissipates the engine heat to the air, the water coming from the radiator is cooler and goes back into the engine.
A bad thermostat needs a water temp gauge to verify.
Heater hose can be very hot if there is full flow in them.
Would suggest a temp gauge be installed, if you do not want one in the dash then mount one in the engine compartment.
Or if none is wanted at all at least buy a HF handheld IR temp sensor, it can not measure direct water temperature but will measure approximate temps on the thermostat housing
