This is common if you have remnants of other Adobe versions. Download the Adobe Creative Cloud Cleaner Tool from the official Adobe site to wipe old files before trying again.
It looks like you’re looking for a guide on how to handle a specific installation package for for macOS. adobe-illustrator-cc-2018-v22-1-0-312-macosx-2-2gb-2022
Before starting, ensure your Mac can run this specific version: This is common if you have remnants of other Adobe versions
This is usually a macOS security feature. You can often fix this by opening Terminal and typing sudo xattr -rd com.apple.quarantine /Applications/Adobe\ Illustrator\ CC\ 2018/Adobe\ Illustrator.app . Before starting, ensure your Mac can run this
If you are using a Mac with an Apple Silicon (M1/M2/M3) chip , this 2018 version is not natively supported. It may run via Rosetta 2, but you will likely experience significant lag or crashes.