Videos produced in Premiere Elements 12

Completed videos can be used as source media in any editing program.   Actual projects from older versions of Premiere Elements may not work in newer versions.  The reason is that features and effects change.  So, if a particular feature or effect was used on your PrE 12 version that is not included in the 2018 version, the project may "corrupt".   

The history in this forum has reports of it both working and not working.  If you try it, be sure to use a copy of the project file in the newer version because in the worst case it will not only not work, but also corrupt the file.  

For projects that are on going, it may be the best practice to continue them in the version they were born in.   You can keep multiple versions on a computer.  They don't share any of their parts.