To resume this post:
If you have just one version installed ( the stable), switch offline as soon as you needn't to use multiplayer. In this way, even if you have a lost of connection, you can use DCS as you want.
It wasn't the case before and at these times, we had just 3 days to use DCS before it was locked until the recover of a connexion. I was very angry against ED for that as plenty of other users were. Now these bad times are over and ED has heard us and found the good solution.
It's quite normal to ED to protect their work with protection as soon as the user isn't penalized by a connection lost. The solution they've found with the Online/Offline mode is perfect for me.
Now, about the 2 versions installed ( stable and bêta):
You can't have at the same time, the both switched on OFF.
If one is OFF, the other is ON. Be careful if you launch the version switched on ON, it will automatically switch the other on ON too and you have to switch again yourself the one you want to use in OFF. It's not quite prudent to keep the both on ON, because if you have a lost of connection while you are in ONline mode, it's back to the old system and if you don't recover your connection after 3 days, you can't use DCS anymore until having internet again.