Most widely accepted rules in Go?

I only know of two different sets of rules (commonly called the Chinese version and the Japanese version), but they play exactly the same. Their only difference is in scoring, and 99% of the time, the same player will end up the winner using either rule system.

1) The first piece can be placed anywhere.

2) No. After the first several pieces have been placed by each player, it is generally wises to place your pieces either adjacent or diagonal to one of your own pieces, but it is not a requirement.

2a) There are only 2 restrictions on where you can place your stones: Firstly, you cannot place in a location that will immediately make one or more of your stones be captured, even before your opponent plays. Secondly, if your opponent just captured a single one of your stones on their previous turn, you cannot replace that stone, even if it would result in capturing one of their stones (to avoid repetition; This stone can be replaced on subsequent turns).

3) Because going first is an advantage (and a desire to avoid draws), the player that goes second gets a 0.5 stone advantage in scoring. Other handicaps are acceptable to be added on to this for either player, so long as they are agreed upon before the first stone is placed. Typically, when an experienced player is playing a teaching game with a novice, the novice is given something like a 5 stone advantage on handicap.

4) Play ends when both players choose on consecutive turns to not play a stone, and passes their turn.