I was planning on running the game when RF 4 Special came out, but I noticed the rules section doesn't include any rules. What are they?
Because mods are lazy, rules are: Using of all glitches are allowed. Time start at the first frame of hitting the "New Game" button and ends at the final hit of Ethelwill.
Difficulty matters a lot.
The main differences have to do with enemy aggression and damage modifiers. On Hell, there's a 25% damage penalty to damage dealt by the player, and a 25% buff to damage dealt by enemies. On Easy, enemies have about a 40% damage penalty and their aggression is lowered sharply. There are also some mechanics changes on Hard/Hell, such as poison ticks being able to KO.
So no, the difficulties are actually a fair bit different and are not comparable. FWIW, the top runs are done on Hell currently. That's not because it's faster, but because that's the more interesting way to play the game IMO.