Why wasn't Krillin permitted to train with King Kai?

[Angelus]

Krillin died and stayed dead for an amount of time after Frieza killed him. Yet was it implied in the manga that Krillin went to King Kai for training? I know it was only 3 months that Krillin was dead but heck, Goku didn't get that much training from King Kai either because Goku wasted most of his time running through Snake Way.

At this point, Kami was already alive again. Does this mean that Tien, Yamcha, and Chiaotzu only got their special King Kai training because Kami personally asked for permission to have them do so, from King Yemma? And Kami was busy during the Namek saga, and not to mention, also alive so he couldn't speak with King Yemma. So Tien, Yamcha, and Chiaotzu weren't automatically considered as "heroes" after their death then? Krillin put in the same amount of heroism Yamcha, Tien, and Chiaotzu showed when he defended Earth from the Saiyans.

[Super Saiyan Turlast x4]

I'm guessing it wasn't necessary for him to train with Kaio at that point. Super Saiyan Goku was fighting with Freeza and eventually the battle ended. It seemed like Piccolo and the humans were training for the possibility of being summoned to namek to fight with the others. Basically, Krillin getting trained by Kaio wasn't a priority. Not to mention he was so much more powerful than Kaio by that point. At least Piccolo and the others were still around Kaio's level when their training started.

[Hitiro]

I assume Kuririn was sent off somewhere else when he died as he died in another part of the universe. Like how there are 4 Kaio's and 4 Kaio planets they may have been in a different galaxy than the one the Kaio we know belongs to. I mean you could strike it as odd that Kaio didn't know where Goku was after he "died" because surely with the amount of power Goku had he could have arrived at Kaio's planet quite quickly. Yet all the time that passed between the Porunga being summoned and Goku never arrived there. It was only then that they found Goku wasn't dead. So I would assume the Kaio just thought Goku wasn't allowed to come his way due the region of the universe he died in.