Old vs New Tax regime

No u can not file by opting sec 115 BAC if form 16 filed as per old tax regime

Any reference.. circular..

If an individual who has opted for old tax regime with his/her employer for TDS on salary, plans to opt new tax regime at the time of filing ITR, then he/she can do that by filling the new form I.e. form 10 - IE but if employer failed to file new form then assessee can not take the benefit of new tax regime.

Yes you can file

Yes you can file , as per your choice