With 4D v18 Beta available it can be exciting to attempt to use it right away to test it's new features. It can also be useful to preemptivly test a database by converting it to v18.

When converting to v18 it is possible to go back to an older version with some prepreation set in place.
A conversion will modify the structure file, meaning a structure file opened in v18 cannot be opened in an older version of 4D, such as v17.

The data file, however will only get converted if the data file is from v14 or older.

So if the database is currently on a version of 4D newer than v14, as long as a copy of the structure file for that version is maintained, the datafile can be opened with any version of 4D over v14.