Musescore saving issues

I am having lots of issues when saving with version 4. After working on a sheet for about an hour Musescore crashed, saving nothing (the old version used to load up an autosave if I remember correctly?) I then started saving after like literally every 2 bars to make sure it wouldn't happen again. Just closed the file and reopened it and all the progress I made has gone. File uploaded for reference - this was an old musescore file that I was working on adding a new tenor line to but yeah it's now all completely gone after hours of work. Extremely frustrating. Is there any way to download version 3, would much rather just use that?