I'd just make sure you have time and date stamps on your files. Like on your computer. Then if you post on somewhere like here you also have time and date stamps.
It occurs to me I may have been taking something for granted that I shouldn't, here.
The absolute minimum safe number of backup copies to have of something you are working on is three, one of which lives in a different geographical location from the other two. A trusted friend or beta, or a dedicated gmail account for sending things to yourself, will work for that. If you do that sensibly the time and datestamps should happen automatically.