Save Project File AS routinely, giving it a unique # or name, so as not to overwrite prior saves. Using Save Project Files (no AS) will overwrite. From the HOME tab, that choice is available by clicking the chevron to the right of the Save Project button on the toolbar. Then you're protected. Click the VPJ and the project will load in ANY VP version. The exception is that projects saved in a very recent version may not load in an older release.
For licensed users upgrades are free for up to six months from purchase date. After that, VP will continue to fully function but a fee will be required in order to register the newest. Retain your old install file and registration info. There's no need to redo the project, provided it was saved as above.