I have done fybsc (p.c.m) in the year 1997. but could not comeplete the graduation then, i want to finish the same, what are my best options

It depend on university decision , can be checked at university through college . any way I am sure registration is valid for graduation only for six tears . you can continue your studies with in six years . further extension can be obtain form university only . But you can do again registration for

If you have completed BSc in PCM then first year then please complete the same in two years instead of wasting one year again by joining BSc in SC of BCA.