This tool can easily unlock specific or all (As of April 23) puzzle swap pieces, edit your hits, tickets, and more by just clicking a button. You need to dump your "meet.dat" save file first, though.

To extract the file, just install JKSV, open it, go to System Titles, and export. You can find the file in the JKSV folder.

Prerequisites:

• You need to install the latest update for Mii Plaza. (ver 4.1 for US, ver 4.0 others)
• You also need to turn on Spotpass updates for Mii Plaza for the latest Puzzles to appear.

How use the program:

• Warning: Please create a back-up. This tool was tested using a EU 3DS, but will work on all other consoles too. This tool will AUTO-SAVE the file upon clicking the UNLOCK button, so please be careful (Although nothing will happen, it will just unlock the puzzle, even if you don't want to.)
• Open the program and hit File > Open Save File.
• Locate the "meet.dat" file.
• Click the "UNLOCK" button on the puzzle you want to unlock. If you want to unlock all, go to Tab 7, and UNLOCK ALL is at the bottom.
• At the last tab (*), you can edit your Streetpass Hits, Tickets, Accomplishments, Streetpass Map, and ability to delete all puzzle pieces.

For Warrior's Way Save Editor:

• You need to get the file called "mgBtl0.dat" via JKSV (Export Street Pass Plaza's EXTDATA Instead)
• Open the program and hit File > Open Warrior's Way Save File.
• Locate the "mgBtl0.dat" file.
• Edit your wanted values, and click "Edit Save".
• Note: If the edit didn't worked, then you probably needed to edit "mgBtl1.dat" instead, or you can simply copy "mgBtl0.dat" and rename it to "mgBtl1.dat".

Version 1.01 (April 23, 2016):

• Added the new Kirby puzzle.

Download Link:
https://mega.nz/#!oF1ViCjb!IhLHwIePD8i2K8xAdx7iIQYOc8MXzIrph1ivhy2nnro

Source: https://mega.nz/#!VUcGWQYK!6fcqh_ZJoOcvK5MRPMUlbfc-6zm8GogLNe0enYmyJRU

If you have any suggestions, or if you happen to see any bugs, please tell me so I can look into it. Thanks!

Credits to Khromasoul (3dshacks reddit) for the puzzle offsets!