Some of my users may want, before finally migrate to QGIS3 LTR, to read with QGIS2 some qgs project files made under QGIS3. I would recommend them not to do that.
But, for the sake of clarity:
- How is backward compatible a qgs file from QGIS3 to QGIS2 ?
- In this old post, there is a proposed answer by Underdark, for a QGIS 2.6/2.2 case. Would the answer be the same in my case?