Will having Japanese game achievements (Mushihimesama HD) on your online Profile cause you to get your account banned or profile rest?. As wouldnt this suggest a flashed drive if these type of Japanese achievements appear on a PAL console/profile as the games are region locked??
Many of the gamerscore beasts have achievements from many region-locked games, so it is possible to get those achievements legitly. Of course, they also have multiple consoles. You could be found out, but only if your account is investigated.
Nope you could have played on a JPN 360, it doesn't suggest any modification was done to play that game.