Hello, You can apply for NET exam if you fall under the age category required to give exam. It does not have any relation to which year you cleared your exam of MSc. Age limit for CSIR net is 28 years and up to 5 years extended for female candidate. UGC net  for JRF age limit is 31 years and up to 5 years extension for female candidate and no age limit to apply for Assistant Professor. You can apply for life sciences in CSIR net. All the best.