Hello,

in one time you can pursue one degree. if you have completed your UG then apply for PG then for PhD in the philosophy. this is the learning path which is followed for every stream. In UG, students read basics and domains of one stream. In PG or Master's, students pursue one domain of the very same stream. In PhD, they work on finding new theory or innovative rules, methods and operation of the very same domain they studied.

you can pursue same subjects from UG -> PG -> PhD but one degree is done at one time.

Hope it helps!