CX-5 to a Mazda 3 aftermarket

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2021 CX-30 Prem
I'm gonna be downgrading from a 2014 CX-5 GT which I went ahead and did an aftermarket Pioneer install in. I'm looking at only the 2012-2013 Mazda3, as those have the Skyactiv engines which get 28/40 and can't go with the 2014 due to the new dash radio. A few questions I have...

Will the wiring harness for PAC RP4, and CX-5 work on the 3 or will I need a new wiring harness?
Are the vehicle settings tied into the radio the same way they are on the CX-5?
I noticed on some Mazda3 they have 2 displays in the dash. One for the radio and one for the car info. I know removing the factory radio eliminates the smaller LCD screen, but what about the other one...is it just tied to the steering wheel INFO button?
The 2012-2013 Mazda3 do not have integrated backup cams correct?

If all this is correct, I should only need the dash kit, and an aftermarket backup cam, to replicate the install I had on my CX-5 correct?
 
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