Buy the Android or iOS version ($9.99). It is literally the DS version with touch controls and can be played on the exact same device you would use for emulation.
While the desire to play this classic for free is understandable, searching for QR codes and ROMs from random sources exposes you to significant risks. chrono trigger ds rom qr code link
Note: You should only download ROMs for games that you legally own. Supporting the official releases—like the version currently available on Steam or mobile—is the best way to show Square Enix that there is still a massive demand for the Chrono series. Buy the Android or iOS version ($9
Once scanned, the 3DS will prompt you to install the title. Press A to confirm. Note: You should only download ROMs for games
The rise of "QR code links" for ROMs is largely driven by the on modded Nintendo 3DS systems. This allows users to "Remote Install" games directly to their console by scanning a code with the 3DS camera, bypassing the need to plug an SD card into a computer.
If you absolutely want to use an emulator like (Android) or melonDS (PC) for the DS-exclusive dual-screen experience, here is the legal workflow: