Vermetid Snails - they are considered a pest. They have a hard shell. They protrude a web that looks like silk or a spider web to catch food. Depending on the coral,and quantity of them they can be an irritant. You can snap them off but do it from the side so they don't poke you. As mentioned before, they have a hard shell and are pokey too. They you may see them growing out of your rock work as well.
Yeah, I see sponges, bubble algae, some other algae, and some spirorbid worms (I’m not seeing any vermetids here, but they may be there somewhere).
Unless they’re invasive and start growing over your corals, the sponges are harmless filter feeders; the spirorbid worms are harmless filter feeders too; it’s generally recommended to remove algae, especially bubble algae as bubble algae tends to be invasive.