How to download and use Mac OS 12 Monterey or Mac OS 26 Tahoe on a 2014 MacBook Pro Retina running MacOS Big Sur 11.07.10?

I am unable to use certain Apps such as Signal in my Mac OS Big Sur 11.07.10. All my efforts to download Mac OS 12 Monterey or Mac OS 26 Tahoe are not working at all. Any workable suggestions will be greatly appreciated!

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Original Title: My 2014 MacBook Pro Retina is currently running MacOS Big Sur 11.07.10. How can I download and use the latest Mac OS 26 Tahoe or Mac OS 12 Monterey?