All versions have English, and all versions will run on either PAL or NTSC systems.
US version had English, Spanish and Portuguese (Brazil was a big Mega Drive market)
EU version had English, German, and French
JPN version is English, and Japanese
And yes the shape of the JPN Pier Solar cartridge will fit both the US Genesis and EU MegaDrive systems.
Well over a year ago, when all 3 versions were still available I pre-ordered the JPN version.