Probably not - while opening a scene that used an old Corona version into a new Corona version is something we aim to have working, opening something from a new Corona version in an old Corona version often will not work. This is because there are new parameters, settings, dropdown lists have a different number of items in them, etc. With so many new solvers (adaptive env sampler, blue noise sampler, 4K Cache) in this version, it would definitely not be recommended to open a scene saved using Corona 6 into Corona 5.