Maven Questions

Given that,

There are three lifecycle phases:

• clean
• default
• site

And within each lifecylcle, there are multiple phases.

• clean
  • pre-clean
  • clean
  • post-clean
• default
  • validate
  • initialize
  • ...
  • compile
  • ...
  • test-compile
  • ...
  • test
  • ...
  • package
  • ...
  • integration-test
  • ...
  • verify
  • install
  • deploy

Questions

1. when invoking a goal, can it be skipped? E.g. can test be called without it invoking compile?
2. for multi module projects, how does it manage dependencies between modules? does it install sub modules first?
3. how does maven manage SNAPSHOT etc versioning? what's the best practise?