What Am I Riddles

Question: Some use me, while others do not.
Some remember, while others have forgot.
For profit and gain I'm used expertly, I can't be picked off the ground or tossed in the sea.
Only gained through patience and time, can you unravel my rhyme?

Question: Walk on the living, they don't even mumble.
But walk on the dead, they mutter and grumble.

What are they?

Question: I grow from trees and your home,
once I am grown I fall to my doom.

What am I?

Question: I'm not a pool, a tree, a slave, a website, or a shirt.

What am I?

Question: Who hunts in a crowd, who hides in plain sight, who do you trust even though you don't know him?