Suppose the ambient air temp. is 20degree C. I need indoor temp. of 26deg. C. I have an AC which I normally using in summer. It was sufficinet to cool air from ambient temp of 48 deg C to indoor temp of 24 degree. C.
RH 50%,
Refrigerant R22.
Is it possible and how?

Are you asking whether a standard A/C unit can be run as a heat pump? The answer is no, at least not without significant modifications to the system. A heat pump is basically an A/C system running in reverse, but it requires a completely different set of plumbing, compressors, expansion valves, etc. You may want to talk to an HVAC contractor to see what's possible with your particular system. What form of heat system are you currently running, and to be direct - if ambient is 20C why do you need heat at all?

This system is marketed as either dual fuel or hybrid.

There is the possibility that a compressor used in a HP system is the same as used with an AC, but likely there is some optimization that takes place in the design.

The major portion of the cost is the labor to add a reversing valve. This changes the refrigerent flow direction in the compressor. This is a LOT of work to add.