yes you will

It is unlikely that it could be used as is, but it could probably be used to apply for civilian certification. Even military pilots have to get civilian pilot certificates if they wish to fly non-military aircraft. Check with your state licensing board.

Certification can refer to many different things. If you know the name of the agency, state office or other entity that provided the certification, you should contact them with your questions about getting the certification re-instated. If it has to do with licensing to offer certain services in your state, there is probably a licensing board or office.

Teacher certification is handled by the 50 states. There is no national or federal certification.

The cost of an ophthalmologist certification can vary depending on your state. You need to contact your state's board of licensing for information on this.