I have spent a lot of time the past few days trying to find information online about the different hand ranking systems available.
Either I'm a Google search dummy or it is really difficult to find out anything about these systems (i.e. what methodology they used to rank the hands).

My curiosity comes from looking at how different applications include different hands in a given range. I've also noticed, that some of the hand charts provided in the strategy sections of this site will include (or exclude) hands in a range that don't seem to match any hand ranking system I've come across yet. I'm not debating the hand selection in any of these rankings/ranges - even though there is quite a bit of variation in them.

1) What Hand Ranking System does Equilab use by default?

2) Any general thoughts on 'Sklansky-Chubukov' vs 'Poker-Stove (vs 3-Random)' vs 'Power Push/Call' vs 'Domination' vs 'Hood-Stox' vs 'ProPokerTools', etc...

3) Any idea where I could find more information on these systems in a general sense (I am no math wiz and the mathematical proofs that may be employed would be lost on me). I did find good info on Sklansky-Chubukov, Poker-Stove and No-Fold'Em systems.

4) Without understanding exactly how the suggested Open Raising Charts were determined (based on them not matching a known hand ranking system), if I want to reduce the given range by say 10% - how do I determine which are the bottom 10% of hands in the included range?

[DISCLAIMER:] I understand that ranking hands from 1 to 169 is situation dependent and somewhat academic. I also understand that when confronted with a situation we should try to define both our opponent's and our ranges based on all the variables present and that this will rarely line up perfectly with any pre-defined hand ranking system.