Officially, no. Microsoft only provides the latest Windows 10 build (22H2) via its Media Creation Tool. Unofficially, you can find archived ISOs on trusted third-party archives, but verify SHA-1 hashes to ensure they aren’t tampered with.
For Build 10240, activation depends on the installation method: windows 10 pro build 10240 product key
Yes, using tools like ProduKey or NirSoft’s utilities. But the key shown is often the generic installation key or a digitally-deposited license. You may not be able to reuse it on another PC. Officially, no