Is all my data encrypted if I turn on a VPN on my iPhone and then turn on personal hotspot and connect my PC?
No. Vpn does not pass through hotspot it has a separate network adaptor.
It does on Android, so I’d assume the same for iPhone.
You can test it like this. On your phone, google for “what’s my IP”, get your IP. Connect via hotspot, do the same, and you should have your answer.
No, your PC will not be in the VPN tunnel
Is there any way to do this? I don’t want to download it on pc
There is a jailbreak tweak that allows it, otherwise you are out of luck unless you install it on your router.