radio install

So I’m replacing my cars radio, and in the user manual for the wiring of the new radio, it says to test the radio (before installation) it says the ACC wire and the 12+ V wire should touch the positive pole of the battery and the ground wire should touch the negative pole in order to turn on...

So I had this great idea to replace my factory deck with a aftermarket. I can get the deck to power on when I hook both the constant and the accessories wire to the battery cable. I am assuming this is the red/white wire is constant power. On the new harness the yellow cable is labeled batter. I...