Simple answer is that on your iPhone your Wifi OR Bluetooth NEED to be on (doesn’t have to be both) and on the other device the Wifi or Bluetooth also needs to be on (again, not both). Put another way: your iPhone is being used as a communication device (either via Wifi or BT), so it needs to be ‘On’… likewise, the device you want to be able to connect TO the iPhone needs to be ON in order to connect (via Wifi or BT). Apple is probably a little more stringent on security that Android…

Not sure I fully understand your question, so I am going to state what I “think” it might be, in case this might be helpful. I “think” you are asking why, if you want to use your iPhone as the ‘hotspot’ for another device to connect to it, why you need to enable Wifi/BT on the other device as well. IF that is the question, then I think the answer is that the hotspot connection goes thru either the Wifi or BT connection (depending which you select). Put another way… your phone connects to the second device either via Wifi or bluetooth… and in order to connect to that other device Wifi (or BT) has to be on/enabled on that other device. If I didn’t understand your question correctly… my apologies!

Definitely WITH a case! I find the phone itself to be ‘slippery’ and while the case helps protect it, for me the more important thing is that it improves the ‘grippiness’ of the phone making me less likely to drop it!