Good Riddles

Question: I have a name that's not mine,
and no one cares about me in their prime.
People cry at my sight,
and lie by me all day and night.

What am I?

Question: Two people are born at the same moment, but they don't have the same birthdays.

How could this be?

Question: I can be used to build castles,
but I crumble in your hands.
I can help a man see,
and am found all around the lands.

What am I?

Question: A man wants to buy a used car. He finds a beautiful Buick for $9500, but he buys it without paying a dime.

How did he manage this?

Question: I'm in everybody but everybody still wants me.
I won't feed you but I'll feed the tree.

What am I?