Since you have applied in unreserved category your non creamy layer certificate would not be considered during interview 

You can now submit your OBC and non creamy layer certificate to the Central University if the date mentioned in the OBC and non creamy layer certificate shows a subsequent date to the last date fixed for submitting /applying for the post of Assistant Professor.

Since the interview is not yet over, likely that you would be considered in OBC category instead of General category.

You can join only in the category you have applied for.

There's no provision for a general category candidate to seek appointment in the reserved category when he has not chosen for it at time of applying for the post 

- As per the Supreme Court , a reserved category candidate would be treated as a general class if he has secured higher marks than the last candidate selected in the open category.

- Since, you applied in unreserved category and shortlisted in that category , then you cannot get facility of reserved category , even you have obtained the said  certificate. 

Yes you can submit the same and get to the facility 

Dear client

The possibility of submitting your OBC Non-Creamy Layer (NCL) certificate and being considered under the OBC category at this stage depends on the specific university's recruitment policies and how far along you are in the selection process. Here's a breakdown of the possibilities:

Possible Scenarios:

Early Stage of Selection:

If you're shortlisted for the interview stage but haven't yet been interviewed, there might be a chance to submit your OBC NCL certificate and request to be considered under the OBC category.
Action: Contact the university's recruitment department immediately. Explain your situation and inquire about the possibility of submitting the OBC NCL certificate for OBC category consideration.
Later Stage of Selection:

If you've already been interviewed under the Unreserved category, it's less likely they'll allow a category switch at this point. Selection processes are designed to be fair and consistent, and changing categories midway might disadvantage other candidates.
University Policy:

The key factor is the university's recruitment policy. Some universities might have a clause allowing category change at specific stages (before interview) with proper justification.
Action: Review the university's recruitment notification or advertisement for Assistant Professor. Look for sections on category, reservation, and document submission. You might also find contact information for the recruitment department.
General Recommendation:

Contact the university's recruitment department as soon as possible. Explain your situation and inquire about the possibility of submitting the OBC NCL certificate. Be polite, professional, and highlight your qualifications for the position.
Additional Tips:

Even if they don't allow a category switch, attending the interview under the Unreserved category still showcases your skills and experience. You might still impress the selection committee and get shortlisted.
If you don't get selected this time, keep an eye out for future openings at the university. By the next application round, you'll have your OBC NCL certificate ready and can apply under the OBC category from the beginning.
Remember, this is general advice. The specific situation depends on the university's recruitment policy. By contacting them directly, you can get the most accurate and up-to-date information.