Income tax

It seems your OPC is not registered with any of the governmental agencies, and doesn't have PAN!!

Sir,

My OPC has registred under MCA and having PAN & TAN also....

OK but your statment as:

"Person "A" having also pharmaceuticals marketing  company (one person company) without sales tax registration and drug licences." 

creats doubt.

Well, it is separate entity, and it need to get its accounts audited and need to file returns every year with the registrar of companies like any other company.

Both the ITRs for OPC and proprietorship firm will be independent, even though you may have same address, as PAN differs.

Would be advisable to borrow services of any consultant, as accouting, its audit and issue with sales tax/VAT department seems to be critical.