From my experience hiring at large corporations, the degree you get is counted as "experience". So someone who completed a 2 year master's degree right after their bachelor's is considered to be equivalent to someone who has a few years of work experience.

In short, no it doesn't matter. Someone without a degree can earn as much as those with advanced ones.

Only if you can get into Microsoft Research. I know a H-1B phD at Google that wasn't making much. I also know a phd at Microsoft doing test... He was making peanuts!

In my experience a MSc often pays more, but a PhD sometimes pays less--some people equate a PhD with someone who prefers theory to shipping code.

Personally I value work experience, solid demonstrable code (ie, what you've posted on Github), and a good attitude above degrees.