I am planning to purchase this Automatic robot kit and modify it into a lawn mower robot of this kind Automatic lawn mower. The modification includes:
-Body (chassis) into a bigger one
-Bigger wheels
-Replacement of all the driving motors included in the kit with 12v gear motors
-Replacement of solar panel in the kit with 12v output panel
-Replacement of battery with 12v rechargeable battery
-Addition of another motor for grass cutting purposes

Is it possible to use the same configuration and electronics circuits and components provided in kit and make the listed changes?

 

The first big challenge will be in the change to a 12 volt system with more powerful motors, because none of the control components will be able to handle the greater current of the more powerful motors.

Yes, I could rebuild an old Dodge Dart vehicle into a Corvette, but the effort and expense would be rather HUGE.

Possibly the control logic could interface with the new hardware to produce a lawnmower robot, and it is an interesting concept. You could do it, but the project would not be simple at all, nor would it be cheap.