Brainteasers!

1. I have been walked on all of my life.I am solid to the core
Words can't hurt me. At times I can be polished up
What am I?

2. I live upon a star. My initials are PQRS. I have many neighbors. I am on something elecric. What am I?

3. A man died of old age, but was only 15. How is this possible?

4. I am the start of war and end of sorrow.
you can't express wisdom without me but I am at the heart of dimwits. You may find me in waves but never in oceans?

Answers
1. A wooden floor. 2. Number 7 on telephone. 3. He was born on a leap year. 4. The letter W