If the native Terminal command defaults to 10.15.7, open-source tools like or MIST (macOS Installer Streaming Tool) allow you to parse Apple's public software update catalogs ( sucatalog ) to find exact build numbers.
Before you do anything else, perform a complete backup of your old Mac's current system and all your important files. Use Time Machine or another backup method. This is a non-negotiable safety step. Data loss can and does happen during system modifications of this nature. macos catalina 1015 19a583 mac app store dow patched
, which was a major turning point for the platform but caused significant issues for legacy software users. Performance & Stability Review If the native Terminal command defaults to 10
The utility will automatically detect your specific Mac model (e.g., MacBookPro8,1 or iMac11,2). 1 or iMac11