not sure if it works back to version 9.x but onmode -b is meant to revert internal structures
in order to be able to startup database with older version without a restore.
That way, the old binaries might be able to boot the database when it has been converted to 14.x.
(maybe you will need to regenerate the update statistics (as recommended after an upgrade).
You can try this on a converted instance of 9.x to 14.10.
For examples of the onmode -b command, see Syntax of the onmode -b command.. When you revert to the older version, Informix displays messages that tell you when reversion begins and ends. When the reversion is complete, Informix is offline. The reversion utility drops the Informix Version 14.10 system catalog tables and restores compatibility so that you can access the data with the earlier ...
Otherwise, dbimport should work, dbexport should be done with -ss flag in order to get
the same table sizes.
When you want to double check it: Try to generate the table structure (using dbschema from the existing 9.x instance),
make a test DB in new 14.x instance, load the schema with dbaccess and then dbexport -ss and dbimport the test DB
in 9.x instance, just to make sure the syntax has not changed.