In Japan, Operation C is known merely as Contra, spelled in katakana as opposed to kanji (probably since the Gameboy audience skews younger, they didn't want any complicated titles to confuse young kids.) The only difference is that the game offers a stage select from the get-go - you have to enter a code to get these in the other versions.
Once again, Europe gets Probotector instead of Contra. It's the usual changes, although the enemy sprites remain the same.
Also, Konami rereleased several of its older titles in compilation format with Super Gameboy support. Though not released in Japan, it did come out in Europe - while it was still called Probotector, it featured the original human sprite. The below image is from the intro for the compilation:
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