hi aditya

most of the PSUs age limit varies from 25 to 28 either recruiting through GATE or not

s.no     name of PSU   POST name     gen     obc      sc      st

1         BARC               SO                26       29      31      31

2        BBNL                GE                27        30     32       32

3        BEML                MT                NA        NA     NA      NA

4        BHEL                ET                27          30      32       32

5         BPCL               MT                25         28      30        30

so u can go through the list and check whether you are eligible or not, it does not matter you complete your engg. in 5 yeares or 4 years

Yes you can give exam of gate .The main thing is that during counseling you have not backlog.

Otherwise there is no issue whether person is doing his b.tech with back or not.

During counseling not carry baclog