Sense of to exist, be present is attested from c.1300. Meaning to pay for as a treat is from 1821. Phrase stands to reason (1620) is from earlier stands (is constant) with reason. Phrase stand pat is originally from poker (1882); stand down in.
In Expert Mode, Wall of Flesh is seen to be significantly faster than his prior speed, posing map navigating harder as the players are demanded to plan out their routes fasters. In addition, getting pulled by his tongue will inflict additional damage to the player, possibly killing a weakened player.
Killing the Guide by any other means will not spawn the Wall of Flesh. A second Wall of Flesh cannot be summoned if one is currently alive in the world. However, it's possible to consecutively summon the Wall of Flesh on the same world, as long as they are summoned and slain one at a time.