Regarding IS claim:
Not an Arabic speaker myself, but all of the translations I have seen use the word "downed," as opposed to "shot down." There was also some defensiveness today on their part about why everyone is assuming MANPAD. The implication they're putting out, FWIW, is an onboard device. They certainly haven't claimed to have "shot" the aircraft down. Also worth noting here is that, while Egypt's affiliate in the Sinai has had a maybe 75/25 ratio, or at least not-perfectly-accurate profile of responsibility claims, the Central HQ as it were has picked this up whole-heartedly, and they tend to be pretty reliable. They're certainly all-in on this.