If you want to try play on dev version and keep current main version intact there is simple way to do it:
1. copy content of entire foldit directory do another directory ie foldit.dev
2. change line in options.txt "update_group" : "main" to "update_group" : "devprev"
3. run foldit and allow to update
If you want to move solutions between installations just save and share save to yourself then load it in another client.