Bjorn,

Since you already have your hosting paid why not install the Version 2 and use the MSaccess database - this will give allow you to get used to DNN.  What version you end up using is dependent on what features you want. If it is localization then DNN3/4 have that built in but there are some localization modules for DNN2 also.  The main problem you will have with Version 2 is if you want to update to V3/4 there is no simple update path so it is a cut and paste procedure which is not hard in DNN to do any way. There are still many thousands of DNN2 sites running on the internet and a lot of these are using MSaccess database.

You should also find a MySql driver for Version 2 if you wanted to go to sql database. There are a great number of DNN2 modules available free or commercial see

http://www.cathal.co.uk/Default.aspx?tabid=28

there are more free modules in DNN2 but if you update later to DNN3/4 then these modules may not be available for DNN3/4

So if you just want  your own home site then DNN2 will do that without problems and it is highly stable. If you want to play around with the code then DNN2 is much easier to handle. If however you want to setup a large commercial site then yep dnn3/4 or moreso sql database for increasing the speed etc.

That's correct.  The newer versions are also have more modules, features and support. 

-Mark