The difference between the two versions of dgraph 20.* and 1.2.* ? The version number span is too large.
Dgraph bid adieu to SemVer, and embraced CalVer.
You can read all about it here: Why there would be no Dgraph 2.0: Goodbye Semantic Versioning - Dgraph Blog
There would be no Dgraph 2.0. After 4+ years of releasing Dgraph, we have decided to switch away from Semantic Versioning. The next release of Dgraph would be 20.03.0. In this post, we talk about why.