The doors are linked to the past if you go to Cocona village at one point the Celibi shrine will be glowing alowing multiplayer games. Yet the bosses that you beat, some have the same exact slates behind them in correlation to the doors in the future, beat the bosses the doors break then you can access the room.
on the peak of it in a secret area
It opensa secret door in the Eterna Galactic building where you can change rotoms forme.
After you beat the game, there is a secret mission you can choose from the main menu
There is no secret Pokemon in diamond and pearl but there are ways to get Pokemon you cant catch on diamond and pearl. For example manaphy. You must clear the manaphy mission on Pokemon ranger. Goodluck with the game!
to open the door of the 7th gym!
You need the secret key found in Pokemon mansion.
The Pokemon on the doors corispond with the bosses you face in the mission into the temples in the past. Once you defeat one of the bosses, go to the door with that Pokemon's picture on it and it will collapse. But the Pokemon behind the door is not the same as the picture, for instance, behind Drapion's door is a Skuntank.
that Pokemon is not in Pokemon ranger, Pokemon ranger shadows of almia, or Pokemon ranger guardian signs
Pokemon Ranger shadows of almia is a newer Pokemon ranger game
Pokemon Ranger was made before Regigigas, so there is no Regigigas on Pokemon Ranger.
Yes there is. You have to finish everything collect every single Pokemon data, finish ranger net and the Manaphy one. Then you ride the lapras and go in the forest and instantly get a quest.
There are 3 kinds of Pokemon Ranger games, the original Pokemon Ranger, POkemon Ranger:Shadows of Almia, and Pokemon Ranger: Guardian Signs. Hoped this helped!