See Spine docs about using Spine.
Our Spine code was upgraded this week to handle various new Spine 4.0 format features. This includes new atlas format support, new curve interpolation spec in Spine files, and some other bits that have changed since Spine 3.x.
We now seamlessly handle JSONs exported from any Spine 3.x or 4.x versions. There is nothing special for you to do — just export Spine models to JSON as usual, and load by setting