ok you kinda need to trade them from ruby or Sapphire after receiving the rubi and Sapphire in Pokemon fitrered!
Braille, there is no language called "regi" , regi are the three legendary rock Pokemon and regigigas.
you can get every pokemon using codes you can get legendary pokemon such as mew regi's HO-OH Lugia every kind of pokemon
You need to trade for them.
by getting all three regi`s from Pokemon emerald, then you can go in and find the fourth regi. (Regigigas)
I think you can only import them from other versions.
you don't you must trade from Emerald, Sapphire or Ruby.
Not easily.
Actually you're wrong you can NOT get the regis in Pokemon diamond, to get the regis you need Pokemon ruby/Sapphire/emerald you can get all three regis there(regi ice, regi steel, regi rock) althought if you migrate all of the regis onto Pokemon diamond you can get regi gigas(king regi) you will find him in the snowpoint temple after beating the elite four. Thanks hope i helped ^.^
I am guessing you have to get all three so you can get regigigias.
Trade from R/S/E.
In the underwater sealed cave and in the three regi caves
I only know Regi rock,regi ice,regi stell and raquaza