My life would suck without you
what i meant is to take the raikou to another version, delete the leaf green save file, start a new one (so i can get a new raikou), clear the game, get the National Dex, and then trade the previous file´s raikou so i can see the new file´s movements.
what i wonder is: once raikou is roaming but i still haven´t seen it, does it have like a determinate nature/ stats even before i first meet it?
Raikou's nature and IVs will be determined once you first encounter it. However, there is a glitch in third gen games where all roaming Pokemon have really low IVs except for HP. If you want a third gen Raikou with decent IVs, your best bet is the one in Colosseum.