The scripture in question is at:Galatians 6:7+8 "Do not be deceived: God cannot be mocked. A man reaps what he sows. The one who sows to please his sinful nature, from that nature will reap...
If you commit sins, you will reap evil
It literally means as you do unto others, so shall it be done to you.
yes Always its in the Bible
a metaphor. anything you plant now will grow into something bigger , good or bad.