my real trouble is that the seeeduino keeps resetting itself while the servos are moving.. i connected a 7.4V 2000mAh lipo battery to the Vin pin and the servos are all connected to 5V pin.
Your problem is that you can't power multiple servos from the board's +5vdc pin. This voltage comes from the on-board +5vdc voltage regulator and can't supply more then about maybe 500-800ma maximum before it will shutdown in protection mode. That is what is causing your reset problem.
You really need an external DC power supply or external battery of not more then +6vdc (servo max voltage) and I usually recommend a current rating for the external voltage source of one amp per servo. The actual current demand for 12 servos depend on the specific servos used, how much mechanical load is on them and how many are moving at the same time.
Also when you get the proper external DC voltage source, be sure the external voltage source's ground is wired to the Arduino ground.