No i don't think so.
well, you just catch it, it's data will be added -dawn.purple4
to get data on Pokemon in your pokedex, capture the Pokemon unless they are trainers Pokemon then you have to cheat to get trainers Pokemon.
no cuz it is a fourth generation Pokemon and its data is not there in the pokedex
www.legendarypokemon.net has a full pokedex, and details on how to get each pokemon.
it shows the data of Pokemon
It's Manaphy and you can get its Pokedex data from a book at the Pokemon mansion below Hearthome.
Nope. Sorry but it is impossible. You MUST go to a Toys *backwards R* R Us store and go to the game aisle. I am 97% sure that the event is OVER. BUT! If you have someone with a Pokemon diamond, pearl, arceus then you can have that person trade the Pokemon over to your game. THEN once you have the data of Arceus, you can get it by trding over the GTS (global trading system.) (located in Jubilife city).
You cannot get Arceus in Pokémon Emerald because Arceus wasn't made for Pokémon Emerald so there is no data for it within the game. Arceus was only made for Pokémon Diamond and Pearl as well as future games.
You can't Dialga is only in diamond and platinum But If you need to add it to your pokedex Then you go To celestic town and talk to the grandma or elder and she'll give you the data for it.
In Pokemon diamond you finish the main story after you beat the Elite four and champion. But after you get access to an island where there is something called a battle frontier, you can battle other people in that game and collect battle points. I don't believe the pokedex collects data from there but who knows i might be wrong. The main idea they are trying for you to do is finish the National Pokedex which contains 493 Pokemon, you need all the game boy advanced Pokemon games and some trading with your friends. Hope that helps =)
Professor Elm (i think his name is) will give you each a pokedex in the beginning of the game. Seeing Pokemon does not officially add their data to your pokedex. To officially add full data you MUST catch the Pokemon. Sometimes at random points in the game one of the professor's aides will ask you if you've caught at least a certain amount of Pokemon, and if the answer really is yes, he gives you a useful item. Be catching Pokemon!