Unable to download and install Monterey OS system

Try while in Safe Mode.

Use safe mode on your Mac - Apple Support

I am going to guess that you are using Wi-Fi for the downloads. If so, use a wired Ethernet connection instead. Wi-Fi is often just too slow for these very large files and corruption occurs. Then you get that message. If you can't use Ethernet, then you may have to download multiple files until you get a clean one that will install. Good luck.

to add to Ronasara's advice, if ethernet is not possible, you can try and temporarily remove your other devices from the Wi-Fi and move the Mac as close to the router as you can. then try the download again.

Monterey…

macOS Monterey is compatible with these computers - Apple Support

• iMac – all models from late 2015, iMac 16,1 – 20,2
• iMac Pro – all models, iMac Pro 1,1
• MacBook & MacBook Retina – all models from early 2016, MacBook 9,1 – 10,1
• MacBook Pro – all models from early 2015, MacBook Pro 12,1 – 17,1
• MacBookAir – all models from early 2015, MacBook Air 7,1 – 10,1
• Mac Mini – all models from 2014, Mac Mini 7,1 – 9,1
• Mac Pro – all models from 2013, Mac Pro 6,1 – 7,1

https://wpbeaches.com/apple-minimum-system-requirements-for-macos-monterey-12/

https://apps.apple.com/us/app/macos-monterey/id1576738294

macOS Monterey on the App Store (apple.com)

https://apps.apple.com/us/app/macos-monterey/id1576738294?mt=12