Good day all. 

Can clinker SO3 perform the same functions as gypsum SO3 i.e. regulate setting time, control the rate of early strenght development and control shrinkage of cement.

Firstly, it depends on your S/A ratio to see whether there is excess SO3 in your clinker;

Secondly, if there are excess SO3, then, there will be CaSO4. However, the solubility of CaSO4 in clinker  is very low, it is not going to have much effect like Gypsum.

Yes, the SO3 present in the clinker will play a role as setting retarder. But as previous poster noted, the effect is dependant on the solubility of sulphate. If it is linked to alkalis, it will be very solube and active, if not, CaSO4 will not be very active.

I know a plant where gypsum addition in the cement is really low because of SO3 and alkalis in the clinker. Saves some money ;-)