Mew: https://pokemonrevolution.net/forum/viewtopic.php?f=119&t=10217
Celebi: https://pokemonrevolution.net/forum/viewtopic.php?f=119&t=15173
Jirachi: https://pokemonrevolution.net/forum/viewtopic.php?f=119&t=33438
Hope this helps!
but what about the other legandaries such as articuno, zapdos, moltres, mewtwo, entei, raikou, suicune, regirock, regice, registeel and so on
The other legendaries you will be able to meet in game to update pokedex, but you will not be able to catch them.