Hello student

After BSc biology you can appear for GATE exam and for life science it will be beneficial. If you want to to take  admission in Mtech in biotechnology through GATE exam then the choice of biotechnology in GATE exam will be beneficial. If you want to do PHD then life science in GATE exam will give you more advantage.

The rules says no.But you can appear for CSIR  after BSc honours before taking admission in MSC. Even if you cleared the exam will not be eligible to get the fellowship before taking admission in PHD. The net result is valid for 2 years.