Help would've probably been a better place for this. :,]
But, to answer your question, the breedable legends are mewtwo,
deoxys, arceus, genesect, and diancie. I think that's it but it's
possible some mischievous little bugger is slipping my mind.
Moving to help but yeah, Unown will give random Unown eggs, you'll
want to use a wide lens on them ^^
Finhawk already answered the question about legendary's but if it
helps you remember if you ever forget, (minor spoiler alert)