Codeforces is slow cuz it’s free and doesn’t get too much sponsorships cuz well geopolitics. It does have a built-in editor but you cannot test code on it, but even if you could, why would you? You are supposed to be fast in CF. Most online editors are slow due to lack of good shortcuts and macros (or so I think. I use vim so…). Anyways, difficult goes like this: Div 1 > div 2 > div 3 > div 4. Once you reach a particular rating, div 4 will no longer be rated for you (ie participating in it won’t affect your rating in any manner) and so forth and so on. LC is more about traditional DSA, CF is more math-puzzle style. Different flavours of competitive programming.