welcome! The title library of Philips for CD-i you can roughly divide in two sections: Those who don't need the Digital Video Cartridge (DVC), and those who need it. The DVC offers full motion MPEG playback on your cd-i player, and is required to play movies and certain games on CD-i.
If you have a DVC installed, you don't have to worry and you can play all titles (even worldwide, as the CD-i doesn't have region codes.
If you don't, check the front covers of the titles, saying "compact disc interactive" on the right bottom, which means they don't require the DVC. Otherwise they'll say "Digital Video on CD-i", or "Video CD". It's also on the back of the box (at least, it should be

)
Hope this helps.