No. There is no animal that can eat something bigger than itself. A king snake has a stomach and it has limits.
They swallow their prey whole.
Because a snake has no bones.
Snakes are able to unhinge their jaws, which allows them to swallow animals much larger than their heads. After they swallow the animal, their jaw hinge goes back into place.
An anaconda can swallow pretty much anything...
If the snake is big enough it will just unhinge its jaws
Some snakes certainly can. Most poisonous snakes could, for example, and some of the larger constrictors could easily do so also (small constrictors might be able to do so if they were lucky, but for the smallest species the cat's a bigger danger to them than they are to the cat).
To swallow - a couple of minutes. To digest - about a week. Depends on how big the mouse is compared to the snake. A small meal could be swallowed in under a minute and take a day to digest. Average-sized meals can take 10-30 minutes to swallow and take 3-7 days to digest. A very large meal could even take a few hours to swallow and take several weeks to digest.
There is a myth that some snakes will swallow their own tail for the purposes of becoming a wheel shaped snake that can travel by rolling, but that never actually happens.
An anaconda can certainly kill a much larger animal. However, it will be unable to swallow that animal if it is wider than the snake's body.
That is true.
Highly unlikely - deer are vegetarians !