If a player would add mana, instead all players add that mana.
All of the mana is produced by the source of the original mana, not by Mana Abundance.
Any restrictions or riders on the original mana are applied to each player’s mana. If those refer to “you,” they refer to the player who adds that mana.
If two or more permanents with the world supertype are on the battlefield, all but the most recent one are put into their owners’ graveyards. In case of a tie, all are put into their owners’ graveyards.