Bonus Play in God of War doesn't appear in the main menu of the game but it is activated since the player finish the Challenge of The Gods. It allows him to skip the videos during New Game and allows him to select Costumes.
Bonus Play was first implemented in God of War II. This extra game mode allows the player to replay the game on the same difficulty it has been beaten before (or lower).
However, Kratos retains all of his magic powers and health, and is automatically equipped with all the subweapons, including the Blade of Olympus, which can be upgraded during the course of the Bonus Play. However, the treasures or relics (Rage of the Titans, the Amulet of the Fates, the Golden Fleece, and Icarus Wings), are lost, and have to be obtained normally, to balance out gameplay, although Rage of the Titans can be acquired much faster and easier than normal due to the fact Typhon's Bane doesn't need to be reacquired unless the player wants to play through that scenario again.
Bonus Costumes can be selected before beginning the Bonus Play mode, and any or all of the Urns of Power that have been discovered in normal play can be activated. If the player discovers an urn during Bonus Play, he is able to activate it instantaneously.
The Arena of the Fates gameplay is similar to the Bonus Play one, with all the weapons and magics in the same levels they were left, as well as the red orb counter and the Blade of Olympus and Urns of Power (that have been acquired) available.
Kratos begins Bonus Play with all the weapons and magics of the game in the same power levels they were left the last time the normal game was beaten. He won't have Triton's Lance and the Cryptkeeper's Key, however, and they must be acquired in the same ways of the normal game. The red orb counter is reset (zero red orbs at the beginning of the game). Bonus Costumes can be used both in Bonus Play and in the normal game, granting the same bonuses, but they can only be used in a certain difficulty of the normal game after it has been beaten in that difficulty (or in a higher one) at least once.
Bonus Play in God of War III is actually the normal game, in which Kratos must acquire all of his weapons and items throughout the game and upgrade them. What is called a Bonus Play of God of War III is a game in which costumes and/or Godly Possessions are used. They can be used with the condition that they have already been unlocked and that the game has already been beaten in that difficulty (or a higher one) at least once.
However, using costumes or activating godly possessions disables trophies. Also, it is possible to do a glitch that makes Kratos start the game with all weapons at maximum level as long as a specific patch is not installed.
Bonus play in Ghost of Sparta is implemented in a similar way to God of War II, with all of the weapons and magics at the levels they were at the end of the game, along with health, magic, and Thera's Bane bars. The Items (The Skull of Keres, Automaton Gears, the Key of Crete and Poseidon's Trident), however, must be re-acquired in the same ways they are obtained in the normal game (notice that Poseidon's Trident is available since the beginning of the game, since this is the case of the normal game, too). The Relics of the game (Callisto's Armlet, Athena's Owl, Aphrodite's Ambrosia, The King's Ring and The Bonds of Ares) can only be used in this mode and, if found during Bonus Play, can be activated automatically. Like in Chains of Olympus, costumes can be used both in Bonus Play and in the normal game, granting the same bonuses, however they can only be used in a certain difficulty of the normal game after it has already been beaten in that difficulty (or in a higher one) at least once.
Unlike Chains of Olympus, however, the red orb counter is not reset: they are accumulated to be used in the Temple of Zeus and buy content for the game there. The red orb counter is only reseted when a normal game is started, but it's like a different orb counter and won't affect all the other orbs accumulated in Bonus Play or the Combat Arena.
Example: if 432 000 orbs have been accumulated in Bonus Play and in the Arena to be used in the Temple of Zeus but the player decides to begin a new normal game, the orb counter of the normal game will be zero at the beginning, as usual, but if this player decides to play Bonus Play, the Combat Arena or the Temple of Zeus, the orb counter will keep the 432 000 orbs.
The gameplay of the Combat Arena is the same as the Bonus Play one, with all the weapons and magics at the levels they were at the end of the game, and only with Poseidon's Trident in the Items list. All the Relics can be used, along with all the costumes unlocked and the Grave Digger's Shovel, which unlocks the Grave Digger's Costume, can only be used in the Arena.
When playing in Bonus Play, Kratos will begin the game with his Blades and Elemental Powers (Fire of Ares, Ice of Poseidon, Lightning of Zeus and Soul of Hades) in the same power levels they were left when the game was first beaten. The Items (Amulet of Uroborus, Oath Stone of Orkos and Eyes of Truth), however, must be re-acquired through gameplay in the same ways they are acquired in the normal game, but when they are obtained, they are in the same power levels they were left, too. Single Player Bonus Costumes can only be used in this mode, as well as the artifacts ("godly possessions" of Ascension). If an artifact is found during Bonus Play, it can be automatically activated. Trophies are disabled in this mode.
Important: As mentioned above, trophies are disabled and even if the player does their requirements correctly, they will not be unlocked. So don't collect the final artifact needed in this mode, because the trophy No Drake. You Can´t Have These won't be unlocked and will be permanently lost, since it's not possible to re-acquire artifacts after they've been already obtained, not even by beginning a new game.