Upperparts too dark for Pallas's, and wing tip pattern incorrect. This is a Heuglin's Gull, probably 3rd winter.
The third photo is a different bird, based on the billl pattern. Difficult to say what it is from this angle and with only the head in view, but it's not Pallas's. That would show some dark marking on the head and a more strongly yellow billl.
Geoff