It has a rod holder. That may do ok for a flag. There is also a rope around it.
Open 2nd valve. It has one to fill and a 2nd one (together) to deflate.
Very likely would. Bottom is fairly durable, made of rubberized nylon. But I could see shells cutting it.
Thank you for your interest in Sea Eagle Boats. Yes, all our inflatable come with a MSO. (Manufacturers Certificate of Origin.)