I'll do that, but I only see beta versions of CB2 , is it important , there he has a risk of not functioning ?
We're way out of beta. CB 2.0.1 is released. You can find it in the Free downloads section.
If I install CB2 , should I reinstall all the plugins ?
No, just disable any non-core plugins. This is purely a test on a clone of your site (don't do this on your live site) to see if the issue is still there in CB 2.0.
I changed the CSS, my modified file Will compatible with CB2.0 ?
Probably not.
The language files are consistent ls ?
Language file usage and structure has changed. All these details have been on our front page, news articles, and newsletters for months; please refer to them for details.