Hi darkskies,
1. With the standard RadarBox, you will get 12 months free access to the RadarBox Network and you will be able to see all the traffic shared by other RadarBox users, wherever they are in the world. After 12 months, the Network access will cost 5 Euros per month. Network data is delayed by 5 minutes for security reasons.
2. There isn't a "Professional" version of RadarBox, but there is a subscription for access to live Network data, rather than the standard 5 minutes delayed. You won't mix up the two, as professional access is at a professional price - big bucks - and only available to professional and Government organisations.
3. RadarBox will work anywhere in the world. The majority of airliners will show on the map, some will only show in the list (older airliners or those without a modern Mode S fit) and some won't show at all - small light aircraft and helicopters.
Hope this helps :-)