Not at all! While the beta will start as a sandbox, nothing stops you from exporting/importing your notes when we’ll switch to production data.
Bear 2 is compatible with macOS 10.14+
We’ll make a post with all the instructions in a few days!
Backlinks will not be in the first beta, but in a later update. We’re adding those inside the info panel like the Stats and the Table of content 
It’s on our list!