how run pkg_check with a trusted kernel (a bit of forensics) and how to check kernel integrity.

Hi,
I'd like to run pkg_check but from a live usb stick. This because I want to run a trusted kernel.
Maybe I just need to mount the root, mount the other slices and chroot /bin/ksh ?
Also¹, is there a way to download all the installed pkg and check the signs from them ?
Also² , how can I check the kernel integrity ?
thank you.
Cord

Sent with ProtonMail Secure Email.