I am a Belgian national and want to move abroad within Europe for a
few years.  Having renovated a house, I received a special tax rate,
but to comply with the agreement I have to be registered as living a
that address for 3 years.  What is the minimum amount of time per year
I have to live there?  If I return to Belgium at weekends and holidays
does that qualify?

Secondly, I plan to work abroad but hope to keep my position in my
current job (private, multinational company).  (Of course I won't get
paid for it while away) Is there a system whereby I can apply for a
'sabbatical' or career break and be allowed to earn money in another
country during the break?

Will I lose all my unemployment benifit rights, health insurance
rights and other social security benifits once I live abroad?

I know you don't give professional legal advice, but I'm just trying
to find out where to start gathering this information so any links and
information to some or all of the question is appreciated.