Catalina Update Bricked MacBook Air Late 2012

In addition to Kappy's great advice and based on what you're describing it looks like the hard drive has failed. It's very unlikely that (a) the upgrade (not update) to Catalina "bricked" it and (b) the EFI has been corrupted.

Explore the options given here:

https://support.apple.com/en-gb/repair

You should be able to get the HD replaced with a clean OS installed for a reasonable fee. Hopefully you've not suffered too much data loss and you've kept regular back-ups?

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