Pokémon Moon Black 2 , the "solid piece" or official download is typically found as a patch file rather than a pre-patched ROM

The Clean ROM: You must provide your own .nds file of Pokemon Black 2 (Version: English/USA). Apply the Patch: Open your Patcher tool. Select the "Clean" Black 2 ROM as the base. Select the "Moon Black 2" file as the patch. Click "Apply" or "Patch" to create the new game file.

Get a Patching Utility: Use xDelta UI (standard for DS hacks) or an online tool like RomPatcherJS. Apply the Patch: Open your patching tool. Select the Black 2 .nds file as the "Source File." Select the Moon Black 2 .xdelta file as the "Patch File." Click "Patch" to generate your new, playable game file. Game Information & Features

Step 3: How to Patch (The Normal Method)

If you downloaded the small patch file (IPS/UPS) rather than a full ROM, you must apply it to your base game. Do not try to play the patch file directly; it won't work.

Gen 7 Pokemon: Includes Alolan forms and various Pokemon from the Sun and Moon era.