Difficult

This is rectangular, hollow and has a lid, and where you’ll find it you might wonder, it is just six feet under. What is it?

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

What is seen in the middle of March and April that can’t be seen at the beginning or end of either month?

All though I am not a cereal I get sold in a box I am something you wear on your feet not a pair of socks

Riddles and Answers