#1 The green macroalgae is halimeda . It is harmless for the most part. Very large specimens could be an issue as they take in calcium and could compete with corals.
A few strands would not make any significant dent to calcium.
They tend to get brittle and break apart too, so I would not worry about them.
#2 Could be some form of graciliaria
#3 Tiny feather duster / tube worms. They are filter feeders and are harmless to the tank. (Their sharp tubes can scrape your skin though, so be careful handling the rocks).