A:AnswerNo subscription needed but you will need an apple account to verify etc.
Yes, it connects to internet. No phone calls. Different operating system than laptops.. it runs iPadOS (which is pretty great actually).
A:AnswerYes, any Bluetooth headphones will work. The Apple pencil has to be the Apple Pencil Pro. First gen and USB-C version will not work on this particular device, which is a little irritating considering how expensive the pens are. I got mine cheaper than new open box at Best Buy.
A:AnswerI have never attempted this. However, it should work but it would be limited compared to an iPhone. For example, no sharing texts, screens, etc.