Q: Alarm wont shut off and car wont turn on.

If your car is a victim of a flood, it is going to experience a myriad of problems for many years. When water gets into electronic modules, what occurs is unpredictable and difficult to fix. In most cases, a car that has been in a flood is a total and should be placed in a wrecking yard. There are just to many problems that will occur over the next few years. Your alarm system is a good example of one problem with many more to follow. It is just to difficult to make a car that was in a flood to be reliable again.

You have done the right things by unlocking the doors with the key. Since this did not work, it is a strong indicator of exactly what I am speaking of. Even if you replace the module that controls your alarm system, there is no way to know if something else that the module connects to has a short to power or ground and can potentially damage the newly replaced module. You have a hay stack full of needles. You will definitely be able to figure some things out, but most likely there will be too many needles to keep track of and there will many problems waiting to occur at the most opportune time.

Diagnosis of this vehicle will be an ongoing process that will exceed its value.

I apologize for the bad news.