Okay, so I always had the idea in my head that Cell learnt Instant tranmission from observing Goku (I'm a manga reader, never watched the anime). And apparently, the anime explained that when Cell exploded, Cell and Goku's cell merge and he just sorta just learn Instant Transmission which sounds kinda dumb tbh. If you doubt the idea I had in my head at the time, refer back to the chapter where Goku learns Kamehameha from one look at Muten Roshi's when he destroyed his father-in-law's castle and Cell literally has Goku's cell. That was what made sense for me since the version I was reading was the officially translated in Vietnamese and never took a look at the English version. I am posting it here in hope that perhaps someone could use their knowledge to prove me wrong since Youtube comment aren't the best place to discuss Dragon Ball lore.