It looks like your computer has 4 DIMM sockets, so to answer your questions: 1. Yes 2. Yes, they will down clock to 2133Mhz, all though the computer is capable of doing 2400Mhz via XMP profile found in BIOS/UEFI. 3. Technically yes but the manual says it supports 4, 8, 16, 32, and 64 via XMP only so it wouldn't be supported and may cause issues. 4. That question will cause some discussion. I like Crucial RAM from their website but you will get people who want fancy RAM from company A or B. Just make sure its a reputable company and not a no-name one. You can find all the manuals here: https://www.dell.com/support/home/us/en/19/product-support/product/alienware-aurora-r5-desktop/manuals