I've searched it for a long time and eventually written it: JJ2 series overview. I'd be glad if you validate all the information below.

Jazz Jackrabbit 2

• basic version of the game
• developers:
  • Epic Games
  • Orange Games
• publishers:
  • Europe: Project Two Interactive
  • U.S.: Gathering of Developers
• release date: 1998-07-31
• engine version: 1.20 (can be upgraded to 1.23)
• episodes:
  • Formerly a Prince - 6 levels
  • Jazz in Time - 6 levels
  • Flashback - 6 levels
  • Funky Monkeys - 6 levels
  • Shareware Demo - 3 levels
  • Home Cooked Levels - user's levels
• episodes in shareware version:
  • Shareware Demo

Jazz Jackrabbit 2: Holiday Hare

• christmas add-on
• release date: 1998 (only in U.S.)
• engine version: 1.23
• episodes:
  • Holiday Hare ‘98 - 3 christmas levels (evening, night, day)
  • Shareware Demo

Jazz Jackrabbit 2: The Secret Files

• easter add-on
• release date: 1999 (only in Europe)
• engine version: 1.24
• Lori available
• episodes:
  • The Secret Files - 9 levels
  • Home Cooked Levels
• episodes in Polish version:
  • The Secret Files
  • Formerly a Prince
  • Jazz in Time
  • Flashback
  • Funky Monkeys
  • Shareware Demo
  • Home Cooked Levels
• episodes in shareware version:
  • The Secret Files Demo - 2 levels taken from The Secret Files episode
  • Shareware Demo

Jazz Jackrabbit 2: The Christmas Chronicles

• European version of Holiday Hare ‘98
• release date: 2001 (only in Europe)
• engine version: 1.24
• Lori available
• episodes:
  • The Christmas Chronicles (or: Holiday Hare ’98)
  • Home Cooked Levels

Thanks.