iCloud backup that I can’t access, because my phone is locked up.

Worth a try at a Forced Restart

Follow the instructions very carefully, as this is a bit tricky. You may need to repeat this several times.

Force restart iPhone - Apple Support

There are only 2 possible results when you perform a Forced Restart:

1) The phone returns to normal operation

or else.....

2) There is a hardware problem with the phone that will need attention at the Apple Store (make an appointment) or take the phone to an authorized Apple Service shop

You can find authorized service locations using this link: Find Locations

Start here.

iPhone Repair & Service - Apple Support

Backups must occur before catastrophes. After you have a working iPhone, you will be able to access any backup you created before the catastrophe.