probably closer to an hour for a 4x4. its just probably not worth the 9 dollars when you don't know the quality of the product that you are getting. If you magnetize it yourself you save 9 bucks and you know the exact quality of your work.
if you can't understand a tutorial in a video format, trying to understand one in a text format will be even harder. I would recommend looking for more videos on "how to solve a 4x4" or provide more helpful pictures so we actually know what your cube looks like.
Yes you are right. The best way to tell if it is old plastic is to see if the core is a creme/tan color for old plastic and a white/clear color for new plastic.
https://imgur.com/gallery/2p3iA
Hope these pics work!
If not it's stickerless and you can pm me for pics! It's 50 mm!
I will respond to all reasonable offers. Pm me if interested.
Edit: I will also take trades! I am interested in everything but 2x2s!