Is MCI has any control over the change of curriculum or duration or modalities of the MEDICAL UG COURSE?

No. It has no such authority. As per section 19A of the IMC Act, 1956 ,MCI can only recommend to the states and after getting prior approval from the states,MCI will forward it to the union govt (MOH ) which is the deciding authority.

Unless the medico has entered in to any bond with the govt. prior to the admission in to the said course,the medico is not legally bound to do compulsory rural service.
As per existing law, once the internship is satisfactorily completed, a doctor is granted permanent registration.