Hi Kimi, the 1st photo of your mystery cactus looks like a 'San Pedro' to me. I had one a very long time ago. I don't have a clue to the 2nd photo. Good luck!
Second plant looks like Maihueniopsis or another South American member of the Opuntioid subfamily. As previously noted it has been growing in low light and has stretched a bit. Watch out for glochids.