There are numerous science fiction conventions held each year. The website Wikipedia has a list of such conventions and in many cases a link to the appropriate website for the convention. Most conventions will provide details for registering as a guest or as a vendor.

Unfortunately no. Science fiction has been used to describe some of the most blatant fantasy ever.

In fiction, use of conventions leads to expectations.

Orson Scott Card has a wonderful book called How To Write Science Fiction and Fantasy. Ben Bova has a book called The Craft of Writing Science Fiction That Sells. These books may be at your public library or you can buy them on Amazon. They would be very valuable to explain how to write science fiction. You may also want to attend writer's panels at science fiction conventions and meet other authors, publishers and editors.

Science Fiction is a fiction based on science.