Will I be certified as OBC-NCL if I provide the NCL certificate during admission by just giving my caste as OBC while applying for TUEE?

You need to submit the OBC NLC certificate during the online registration. The same will be verified during the admission. 

The college will provide correction facility if caste entered wrongly. In your case you entered OBC instead of OBC NCL. So it's depends upon the college whether accepting your O