It is confusing: Jazz Jackrabbit 2 Holiday Hare '98 (v1.23x) was a U.S. only Christmas promotion Jazz Jackrabbit 2 v1.23 "demonstration" (NOT a downloadable demo as software). Jazz Jackrabbit 2 - The Christmas Chronicles was a modified European version (Poland & The Netherlands) of HH98 and was the same as above - no downloadable demo. So you actually went to a shop and bought a "promo demo" of Jazz Jackrabbit 2 (v1.23), right?
Jazz Jackrabbit 2 - The Secret Files (v1.24) was a European (it got to the U.S.?) stand-alone "add-on" or "expansion" to v1.23. It included all the v1.23 episodes (5), the "Shareware Demo" episode (included in all versions no matter demo or full), the "Holiday Hare '98" episode and a brand new episode called "The Secret Files" with 9 levels.
Please correct me if I'm wrong.