Just cannot believe how I made this difficult for myself, definitely DO NOT overthink it.
USER: was pretty straight forward, you do not need a reverse shell to get what you need.Once you get that file work your MAGIC to solve it.
Root: Like others, I spent hours on this when it could have taken me 2 mins to solve it. Look for files close by, see what is happening.See the relationship between files.
Again, do not overthink it and do yourself a favour: read the manual for that famous command!
Really enjoyed this box.
If you need some help feel free to DM me.