Final Fantasy Adventure was called Mystic Quest in Europe. Would you like a picture of the cartridge? You're confusing the game with another game know as Mystic Quest, Mystic Quest Legend for the SNES (known as Final Fantasy Mystic Quest in America).
Sword of Mana is a remake, you can still find the original game in it, but as lot was added. I mean, be honest to yourself, if they hadn't there wouldn't have been a lot of game to play.
And yes, the game starts almost exactly the same. Castle, gladiator/slave, Jackal... only it's in colour and Willy doesn't die a second after we meet him.
This and
this should bring back some memories. And surely you can remember Wendel, the town of Jadd, Julius, Medusa. Devius? Oh noes, it's spelled differently, surely this cannot be the same character!
Frankly, I think you're an idiot for not recognising al the similarities.