I really should make a Word file on that and paste it after the release of each version
Ok, first things first.
League Structure
Spain has a Pyramidal Football structure. You've got First Division and Second Division (which are the Pro-Footie leagues) and after that it starts to regionalise.
Second Division B is comprised of 4 Groups: I, II, III and IV. The boundaries of those groups vary depending on the teams playing at 2nd B level, but to put it softly we could say I=Center-East, II=North, III= East and IV= Center-South.
The Regular season is made of 38 matchdays and after those are done you get the Promotion play-offs, Relegation Play-Offs and Relegation.
Promotion Play-offs are played among the 4 top on each group (unless there's a B team there which has the A side in Second Division. If that's the case, then the B Side stays in 2nd B and 5th best enters playoffs) and it's made of 3 rounds: Quarters, Semis and Final. Only the winners of each of the 4 finals get promoted to 2nd Division.
Relegation is easy: 4 bottom teams for every group get relegated (unless an A Side which has a B Team in one 2nd B group gets relegated. Then it's the B Team that gets relegated, regardless of its final position, and only the 3 bottom. The 4th bottom gets on Relegation play-offs and the 5th bottom is spared).
Relegation play-offs are played between the 5th worst team (unless there's the A Side getting relegated issue we talked about). You've got semis and final (loser advances round and loser ofthe final gets relegated into 3dr Division).
So that's 17 relegation spots (due to Spanish 3rd comprising 17 groups) and 4 promotion spots.
Cup Structure and eligibility
Not every 2nd Division B team is eligible to play the cup. Teams who get promoted from 3rd Division play it (as prize for promotion). The 5 best teams from last season also play it and teams relegated from 2nd Division to 2nd B as well.
Early rounds are regionalised and it's only when the teams playing Euro Competitions enter that you get a free draw.
Up to Quarters the matches are played at one venue at the lowest classified team place.
hth