SORRY IT FINALLY FAILED!
Steps:
1. Run a game DL Play supported (such as Mario Kart 7, Luigi's Mansion 2, some VCs like Battle City, etc.) with SOURCE 9.2 console - Only Digital version works!
2. Start a multiplay.
3. Run DL Play with TARGET console, choose 3DS mode, then enter the multiplay SOURCE console hosted.
4. Upgrade TARGET's firmware when the dialogue appears.
Steps:
1. Run a game DL Play supported (such as Mario Kart 7, Luigi's Mansion 2, some VCs like Battle City, etc.) with SOURCE 9.2 console - Only Digital version works!
2. Start a multiplay.
3. Run DL Play with TARGET console, choose 3DS mode, then enter the multiplay SOURCE console hosted.
4. Upgrade TARGET's firmware when the dialogue appears.