The following are known Action Replay Codes for Tamagotchi Connection: Corner Shop 3 on Nintendo DS (NDS).

Game ID: YT3E-85C2F013

Max / Infinite Gotchi
02129500 0001869f

Press SELECT: Unlock All Shops
94000130 fffb0000
c0000000 0000000d
22129509 00000001
dc000000 00000010
d2000000 00000000

Press SELECT: Max Customers Helped (All Shops)
94000130 fffb0000
c0000000 0000000d
2212950c 0000000f
2212950d 00000027
dc000000 00000010
d2000000 00000000

Press SELECT: Max Reputation (All Shops)
94000130 fffb0000
c0000000 0000000d
2212950e 0000000f
2212950f 00000027
dc000000 00000010
d2000000 00000000