Car has gone into security mode

You don't magically fix anything by removing a battery cable but you have introduced more problems. The Engine Computer turns on the automatic shutdown relay. If it doesn't do that on its own during engine cranking the engine isn't going to run anyway.

With no punctuation in that huge sentence it can be read at least three different ways. By "no power to the relay", do you mean the relay is not turning on or there is no 12 volts there to be switched on and off? You should find 12 volts on one of the terminals in the socket all the time. If it is missing check the fuses in the under-hood fuse box.

If you do find 12 volts on one terminal, feel that relay while a helper turns the ignition switch on to tell if it's clicking on. It should turn on for one second after the ignition switch is turned on, then again during engine cranking.

The ASD relay should turn on for one second after the ignition switch is turned on, then again during engine cranking. That one second is to run the fuel pump to insure fuel pressure is up for starting. After that the computer turns the relay on when it sees engine rotation, (cranking or running). That's the safety feature built in to shut the fuel pump off if a fuel line gets ruptured in a crash.

If you don't have a helper you can also use a test light to test for voltage to the ignition coil pack or any injector. Usually that is a dark green / orange wire at all five places. Back-probe through the rubber seal alongside the wire. If the test light's probe doesn't make good contact you can disconnect one of those plugs and touch the probe right to the terminal. The test light should light up for one second as soon as you turn the ignition switch to "run", then it will go off again. It should turn back on when you crank the engine. See if that is what happens.