Can patients (age 12) with autism and seizure disorder experience gains in cognitive and social function post seizure activity?

Anything is possible: That is not a common finding. But it certainly is possible.

Yes: yes.with proper therapy it is sometimes possible to see therapy.there are no "magic" cures such as diet or vitamins

Possible: Autism has broad spectrum of disease presentation ,thus it is possible to gain in social function and cognitive function after seizure activity .