A great box, felt like eternity tho. A bit CTFy I believe and I’m not sure why it had the top mark in real-life like. Everything has already been said. My two cents:
Foothold: enumerate - build that tool that supports that protocol - get in - exploit (baby steps! - If somebody has done it in one go, or even two please message me)
user1 → user2: you’ll realise what you need to do early on. Trial and error!
Root: It’s literally home, sweet home!