The clam thing is indeed some type of bivalve but not sure to species. The shell is encrusted with coraline which makes ID tough.

Mushrooms are the genus discosoma and probably species mummiforis and appear to be splitting since their are two mouths.

The other "fuzzy mushroom" appears to be a Rhodactis sp.

Common names are basically completely and utterly useless since they are so variable and ID'ing many corals is limited to Genus if we want to be honest. Most people that put labels on Acropora sp. are usually doing a lot of guess work because Taxonomists will tell you that id'ing many corals requires bleached white skeleton in hand (for those that have skeletons).

Lee