sea weeds small fish
Of course it can. It can eat anything small enough to fit into its mouth that it wants to.
some beta fish are aggressive and will tend to attack other fish but depending one the environment you've had them in they wont. Like if they have been around other fish then no but if they were by...
Yes. They are also able to kill a starfish if being territorial and the body consumed by other tank inhabitants.
nope
Clowns have been known to eat smaller fish, usually fry. Some clowns are more aggressive and therefore more likely to than others so as the Maroon.