You can get Entei and Raikou to come back by defeating the Elite 4 and Lance in Pokémon HeartGold and SoulSilver however this only works if you've defeated them previously. They'll keep on regenerating as long as you beat Lance however once you catch them then they won't regenerate anymore.
train them a lot to around 20
Defeat the Elite four and catch the boat from Olivine to Vermillion
train your pokemon up to level 80,90, or 100 and teach it TMs and HMs
In HeartGold and SoulSilver, there is a red Gyarados that you have to either defeat or capture at Lake of Rage. Other than that, there are no games that do that.
you must defeat the elite 4, after are you going to mt silver again.
Um. You pay him money. Just like every Trainer.
In Pokémon HeartGold and SoulSilver, Professor Oak will give you the National Dex at the port in Olivine City if you have defeated the Champion of the Pokemon League. You also need to go to Prof. Elm and defeat the Kimono Girl's, all of which have evolutions of Evee.
Get Rayquayza if you can (you'll need a Kyogre from HeartGold).
Well after you defeat 15 gym leaders in Pokemon HeartGold / SoulSilver go to Cinnabar Island and talk to Blue.
In the pewter city museum. to get his attantion you must bring walking latias ( heartgold) or latios ( soulsilver ) with a soul dew from a mystery gift. then he will take you to saffron city. he will talk to you for a while. then he will go back to pewter then show you latios ( heartgold ) or latias ( soulsilver ) outside of the museum. then after you defeat or catch one of eon Pokemon that's the last of him.
you have to defeat the elite 4 again, then go 2 Mt. Silver where u first saw Red. he should be there.
If Raikou faints, go to the Burned Tower . Then you see him. Same as the other legendary dogs however Raikou will only regenerate if you defeat the Elite 4 and Lance, once you have caught Raikou, it will no longer regenerate.