High Pitched Tone, ABS, E-Brake, and (!) Lights all Come On

Those are two of the roughly one hundred possibilities that can turn on the lights you are seeing and the symptoms you're describing. That you also get the sonic alarm narrows things down a bit, because only about the half dozen most safety-critical problems are programmed to also sound the alarm. (Neither a wheel speed sensor nor the battery would be in that set.)

You haven't said what code reader you're using. I'm sure you've seen in a lot of the threads you searched that Techstream on a laptop is the most dependable way to read Prius codes, and that many other readers will completely miss codes from some of the computers in the car, and that pretty much always that's what's happening when somebody says "I've got these warning lights and no codes" (because the warning lights don't come on unless there are codes).

If you're kind of impatient about the time to order a J2534 dongle and have it delivered and set up a laptop with Techstream, you probably also saw numerous threads about just using a jumper wire to get the brake computer to blink out two-digit codes on the dash lights. That is less information than you'd get with Techstream, but often it's enough to get you going, and it's nice knowing you've got that way of reading the codes anywhere you are when warning lights come on, even if you might not have a better reading tool with you.

 

In case the OP was uncertain, the presence of the high pitched alarm means that the car should NOT be driven at all, until the root cause is resolved.

 

I had that happen also. My 12v battery was older and I had other weird things happen like the windshield wipers ran very slowly. The problem went away when I cleaned the battery terminals but I replaced the 12v anyway for good measure.