Well
it’s a very long story but it wasn’t on purpose, he wanted to do something else entirely when he was a kid and the master noticed he wasn’t growing up and stuff (that’s how he became “immortal”) so the master shared his life force with Jaegyeom so he could continue growing up like normal. If he stabbed him it was because the master wanted to “defy” his destiny but a situation occurred that made him realized that he really can’t change destiny which is why he stabbed him (tell me if you want me to tell you more, I tried my best to not spoil you too much)
Not exactly. I would say if someone has a "fate" it would be Taehee's character. He has the mark of the hometown and he has a fate to become a god or a hero. MC in the other hand has a calamity God inside and they are just connected by Taehee's dad. But both were not fated and they meantto stay away from each other, according to the hometown. Both they defied what it was intended for them and at the end they chose each other instead of their "destiny "
It did, but I think it was stated that it took a very long time for example the length he had in the beginning was the same for several years because his growth had stopped, and he had even said that he took a long time to heal, etc (with the mermaid and stuff) basically that everything took longer with him (because of the seal), but since he woke up, he said that his hair had grown and everything (in the side stories if I’m not wrong)

Someone spoil me please, why did jaegyo.'s master stab him? And why curse him to be an immortal?