the show with ji-won and kai is called 'new world' it's on netflix. and the drama they are talking about at the end is 'flower grandpa investigation unit'. I really recommend it.

The show you said you want to watch (the one where he's young) is called X-man (ep 106), it's a lovely episode and all are whipped for him haha the newer one (with sniffing pants lol) is netflix show The new world, it' super fun I recommend it

He's sooo beautiful 😍🥰. Like most people have had a glow up since their adolescence/teens and Heechul never even needed one!! Pretty straight out the gate 😅