To get multiplayer on Pokemon Ranger Guardian signs you must meet with Celebi 2 times (I think). Celebi will take you to the past each time and after the second time you will be able to play multiplayer if you go to Cocona Village and tap on Celebi's Monument. It will say: "You feel a strange power... Will you travel through time?" Tap Yes. Celebi will welcome you. Ravio will say: " You're back!" He will get his friends and they will warn you about the temples. They will say what to do.
no regigigas does not
rasp cavern
he is in the sky
in the cave of icicles
yes
pokemon originaly came from there mother
it is in daybreakruins i think
you never use it
you go there at the start of the game
never after shaymin its giratina
in the forest past tilt city, I think?
The only Partner Pokémon in Guardian Signs is Ukulele Pichu. However, you can use certain Ranger Signs you get by completing Quests to summon different Partners to use in the Past for Multiplayer Missions.