Misc: What is the longest living land mammal after man?

Questions

What is the most recent year that can be written upside-down and rightside-up and still look the same?

What is the most rural state in the u.s?

What is the most slippery substance known to man?

What is the most widely spoken member of the Iranian branch of the Indo-Iranian languages, a subfamily of the Indo-European languages?

What is the most widely used seasoning?