FF8 disk compatibility

Right. Due to my idiocy, I recently purchased this off eBay (ff8 platinum ed.) only to discover disk 4 was missing. And the only disk I can find that is less than I paid for the other 3 games is of another edition (not sure which, probably original, has a pic of Edea on the front of it). So my question to any and all is: (you guessed it) will they work together, or am I barking up the wrong tree? (On an unrelated side-note, did anyone else here always call rinoa's dog "sh*t"? bearing in mind i was 13 when i first played it)