Hey Guys...
this is the reply I got when I re-sent my email query to BHC....
You can hold two visas in different categories in your passport, but you must tell the Immigration Officer on arrival in the UK which visa you wish to enter on. Obviously the correct documentation will ease your leave to enter the UK.
You are free to enter the UK within the validity of your visa. Please note that the final authority to enter the UK rests with the visa officer at the port of entry.
Yours faithfully
Casework Team
Finally I have made my mind to apply for my wife's dependant. I'll be applying in next 20 days.
Also, just to update on this forum (so that others looking for similar info may benefit). Few days back, after my first call to VFS, I had called VFS once again, this time a lady answered and her answer was similar to the mail from BHC above.
I am thinking of writing a complaint email to VFS. Some guy from VFS earlier gave false information with solid confidence. Because of which I lost 15 days.