Hello.
The open ended pipe section by the neck of the reservoir cap, what is its function ? Breather; overflow; overpressure relief...? If it burps/drips means what ?
The other one [23] hooks to the radiator left top corner. Is it supposed to keep the radiator with no surface air or to add air ?
The one exiting the throttle body heater [16] enters the reservoir at the bottom. The heater core exit is [9] and also pump suction and also the reservoir exit ?. Please correct me.


Yes, the one not shown below :

[Images borrowed from the web]

 

It's just an overflow, in case pressure in the system exceeds the 15 psi spec of the system and the cap.

 

Slip a hose over it and run it up to the cowl