Powersave
How can I use the "close blender to undo changes" workflow?
Personally I recommend instead just hitting PowerSave to do an incremental save before making any changes you might want to get rid of.
But if you insist, you can use autosave to a separate file, then after reloading your project, not clicking OK on the popup that says the autosave is newer.
Is my OS supported?
PowerSave should run anywhere that blender runs.
I can't see very well, is there an option for high contrast icons?
Yep! There's a checkbox for it in the preferences.