I went down this path as well.

I bought the AVT-852 cable because it was the cheaper option, then used Tuner Po and the 24x7 dimented tool.

It will only write the same OS to the PCM. If you try to flash a different OS it bricks, if you try to flash certain OS partial writes, it bricks.
If you follow all of the steps exactly as they are, and only stick to the 1 OS and have a proper XDF with all of the parameters you need, you might be ok.

Trust me, its A LOT cheaper to just buy HP Tuners.

You can plug and play, read/write tunes, there's a wealth of info and tune repository to choose from on the forums.
I'm a computer guy, and even for me, the amount of shit you have to go through and learn for it all, it's not worth it, and once you brick a couple of PCMs trying to get shit working, it's really not worth the hassle.

Just my AUD$0.0026c