NVivo software provides backward compatibility only.  NVivo project files (.nvp, .nvpx) from newer versions can't be opened in older versions.

Starting with NVivo version 12 however, if your project data consists of only txt, doc and docx files (no pdfs, datasets, audio or video) and you need to work on a project with different versions of NVivo, you may be able to use the REFI-QDA (.qdpx) file format to exchange data.

If the project contains data other than those listed above, all members of the project team need to be on the same version of the software. NOTE:  If you need to continue using the older software for other projects, more than one version can be installed on the same computer.

Please see the directions for using this format and its limitations for non-text data in the Support Search Results below:
QDPX Format (REFI-QDA)