We endeavour to keep every update of Construct 2 backwards compatible wherever feasible. On very rare occasions we make breaking changes, and clearly point them out in the release notes.
Back up your project and then open it in the new version. If you want to go back for some reason, reinstall the older build and open the backup (note if you save in a newer version you can't open in an older version, which is why you should back up). Hopefully though everything will just work smoothly.