Now, since Codechef has announced Integral Problem Difficulty ratings, I have some questions:

How is Problem Difficulty Rating calculated on Codechef?
(For instance, in Codeforces, it is calculated based on how many users were able to solve it in the contest.)

How does CodeChef Problem Difficulty Rating compare with Codeforces? What is approx mapping?
(Ex: What would be the difficulty rating of a problem on Codeforces, whose difficulty rating on CodeChef is 2441 ?)
(I guess that mapping may be like

Codeforces_Rating(x) == Codechef_Rating(x) — k

What is the basic implication of Codechef rating?
(For instance, in Codeforces, Approximately this means that if the rating of the problem is equal to yours, then on a typical round you would solve the problem with a probability of 0.5.
Source : https://codeforces.net/blog/entry/62865 )

For Codeforces problem difficulty ratings, there are many blogs like https://codeforces.net/blog/entry/46304,
but there are none for CodeChef. That is why I resorted to asking about it here.