1.
Friendships are relationships and if two friends share a third party then it is swinging and sharing even if those friends never do anything sexual together.
2. Polycules can be platonic and involve sending pics/videos to each other to get each other off without actually having sex with each other. It seems like this may be what you are going for,

3. I have never seen "just friends" intentionally share pictures or videos of themselves having sex with other unless there was some underlying reason for it that makes the "friendship" idea suspect. Like attempting to make one or more "friends" jealous to get them to desire the sender or otherwise provide sexual gratification to each other which is not a standard friendship either.