can pendant be used for duration in the past using imparfait eg J'etudiais le francais pendant 2 ans

Pendant, in this context, refers to a well defined period in the past. Therefore I would say:

J'ai étudié  le français pendant deux ans.

I don't think there is a rule forbidding the use of imparfait in conjunction with pendant. It's just that in this example, I would use the passé composé.

The opinion of a native speaker would be greatly appreciated, though.

Hi L,

No,  you cannot say,  'J'étudiais le français pendant deux ans.' as it lasted two years in now finished, the only possibility is-

'J'ai étudié le français pendant deux ans.'