Can you buy fish and then put them into your own pond

You can buy koi, catfish, plecos, and some gold fish. There are others too. Just really depends on how big your pond is.

The answer is a definite YES, but there may be restrictions on what type of fish you may keep in a pond especially if the pond is prone to flooding and the overflow can connect to native waterways or if native waterways can overflow and connect to your pond. Fish is too generic a term. It is best you contact the Fish and Wildlife Department as to what species are and are not permitted in the advent of flooding. I can only presume you meant Koi, but Hurricane Florence may have affected their stance on certain fishes. Better safe than sorry. "Pond" is also too generic a term. I have no idea if you meant a small garden pond, or a real pond of decent size fed by natural sources or accumulated rains or ground waters. Still... best you check with the local F&W Dept for specifics. Inadvertent fines can be quite steep if you don't.

Yes

Yes, you can.