Can reserved category students take admission through other reserved category quota?

No. A clear no. Those who are appearing in Government recruitment examinations must understand this complicated rule position regarding reservation clearly. I am trying to explain this provision clearly with the help of an example. A candidate belonging to SC category will be considered against SC vacancies as well as UR (Unreserved) vacancies. But such candidate will not be considered against any other reserved category (OBC or ST) vacancies, even if some of the earmarked posts in those (OBC or ST) categories go vacant.

However, if a particular candidate is covered under reservation for two categories (for example, SC and ex-Serviceman), then he/she will be considered for both types of reserved vacancies as well as UR vacancies.

One can not have both the benefits. A candidate will be considered for the vacancies as per his category of reservation. An OBC candidate can not seek for quota reserved for SC candidate.

There are separate merit lists for different categories and the qualifying score can differ from one category to other but a candidate has no option for switching to other category. One will be considered for the category under which one has applied and he should have necessary documents to support that.

A reserved category student can get a seat in general category by virtue of his marks. The reserved seat will go to another candidate who is from the same reserved category.
But a reserved category seat is not allowed to get a seat from the seats allotted to another reserved category. A BC candidate will get a seat either from merit list or from reserved category. But not from the seats allotted to SC/ST.
General seats are known as unreserved seats. They can be filled by any category provided they are in the merit list.

No. One cannot do that. If a person is reserved under SC category then he or she can take advantage of this category only.

If an OBC category candidate gets his name in the merit list prepared for the general category then it's his will if he wants to take advantage of his reservation or not.

Reservation policy was introduced to provide concession for the different classes such as OBC, SC/ ST, Ex- serviceman etc.
In the event of duality such as father belonging to SC and mother being to OBC, the status of reservation does not allow the candidate to avail of duel concession. He has to stick to either of the two. However, there exists an exception in the case a candidate is enjoying the concession of ex - serviceman and comes within the bracket of ST, he can enjoy the concession of both.