I don't quite understand.
Are you talking B&W or colour?
In either case once processing has taken place then there is nothing left to process.
The only thing you can do with B&W is intensification, where you intensify the image already there. It can help with thin negs but will not have an effect if there is not an image there already.
It tends to involve things like Uranium compounds so it is best avoided.
you can re-expose film once its been exposed, yes. Thats how they do double exposures. But you cannot re-expose film once its been developed.
I think what you are trying to ask is if you can re-develop film that has already been developed? I would assume your thinking is that you would try to improve on the initial develop in order to gain something. The problem is once the film is developed it is then fixed. You got what you got.
If you shoot large format sheet film you can do muliple shots with the same exposure and develop each of them differently to get different effects.