Desktop Hardware and Upgrade Questions

I have a Z4 G4 Workstation, now running Windows 11 Pro, which I purchased in 2018. I am very happy with it but didn't max out it's capabilities when I purchased it. I purposely purchased the Z4 so I could upgrade the processer down the road.

The HP documentation contradicts itself and the help/search doesn't align with the documents. I am not experienced in these deep details of CPU upgrades and learning so any assistance would be appreciated.

The computer motherboard is the HP 81C5 MVB. My current processor is the Xeon W-2125/4 Core that uses the LGA2066 platform. I also currently have 24GB of memory but want to know what the max memory configuration is as well.

1. Where can I find documentation on the HP 81C5 MVB motherboard? Searching the HP site and the internet doesn't provide any insight.
   
   
2. Can I drop in any modern LGA2066 chip, something developed in the last year? Or does it need to stay on a legacy chip that was of the same chipset? 
   
   
3. Does it need to stay Xeon? Or can I go I-9?
   
   
4. Does the particular CPU choice have a limiting factor on the amount of memory?
   
   
5. HP docs and other tools that scan my setup show that between 512GB or 254GB can be installed. So which is it? Why the difference?
   
   • For instance, if I got to Crucial and look for the specs of my computer it states I can install 512GB but doesn't provide state 64GB chips are compatible, even though when I purchase this system, the 64GB chips were. I suspect this is just confusion of the custom setup of the machine.
   • If I look at the spec sheet from 2018, 64GB chips are specified with the Xeon processor as long as a memory cooling block in installed. I have the cooling block.

Appreciate the assist! 

-Aarron