Dragon lore says kneel dragon lore and kneel attached character to do X, is kneeling the attached character part of the cost to do X? If the character is already kneeling can I activate dragon lore's effect? If the effect get cancelled do I have to kneel both the character and dragon lore?

When an effect says "do X to do Y," X is the cost and Y is the result. You have to be able to do X, completely and successfully, in order to trigger the effect. You must also do X, completely and successfully, before anyone has a chance to cancel the effect. And if someone DOES cancel the effect, you don't get to "go backwards" to undo or "take back" your X.

So, specifically to Dragon Lore, kneeling the attachment AND the attached character are part of the cost (both before the "to"). You must kneel BOTH in order to trigger the effect (something you can't do if the character is already kneeling), and if someone cancels the effect after you initiate (ie, kneel them) you don't get to "go backwards" and stand them just because your opponent canceled.