One more question, when two Pendulum Monsters are used to set pendulum scale, if they leave the Field, will they end up in graveyard or extra deck? plus after that will other Monsters, Summoned by Pendulum got destroyed, will they end up in graveyard or extra deck?
1. It does not matter if a Pendulum Monster is actually in a Pendulum Zone as a Spell Card, or in a monster zone as usual. If they are destroyed while on the field, they will go to the Extra Deck unless an effect specifies otherwise.
2. If a Pendulum Summoned monster is destroyed (regardless if the Scales it was summoned under are on the field or not), it will return to the Extra Deck if it is a Pendulum Monster and the Graveyard for everything else.
For an example setup, let's assume that I have Pendulum Summoned Odd-Eyes Pendulum Dragon, Majespecter Unicorn - Kirin and Dark Magician Girl, and then the opponent decides to play Dark Hole/Raigeki or some other field wipe. In this instance, OEPD and Kirin would go back to the Extra Deck because they are Pendulum Monsters, whereas DMG would go to the Graveyard as normal because she isn't a Pendulum.
To be fair, a lot of your questions have the answers on the Yugioh Wikia.