Cant give you a clear answer. I checked the page of Asus and havent seen the board. So I can just speak about the Asus Maximus XI Formula z390 mainboard which according Asus can be used with water and aircooled pc systems.

No, you don't have to, but you can. Greetings

I have installed a 5900x but I recommend that you update the bios to take full advantage of the processor's functionality.

M2 SSDs are passively cooled. I have 2 Samsung 980 Pro in it, max 48°. The fan on the mainboard is only for the chipset.

.....hier mehr infos....https://webshop.asus.com/ch-en/winterdeals-22-23-ch-en

Screws for fixing a motherboard in a case are never supplied with the motherboard. The screws are included in the delivery of the case. https://dlcdnets.asus.com/pub/ASUS/mb/SocketAM4/ROG_CROSSHAIR_VIII_FORMULA/F15393_ROG_CROSSHAIR_VIII_FORMULA_UM_WEB.pdf - Box contents page 15 - where (Slot?) exactly are you trying to insert the M.2 SSD and it doesn't fit?

No, BIOS for the 5th gen is on it.

Sorry the board has two m.2 slots not three, but both are PCI-E 4 compatible.

I don't know the detailed specification of the Dark Hero. As far as I know, the memory clock support of the Dark Hero is even higher - up to 4866, 5000 or 5100 MHz and has a pure PCIe 3.0 x16 slot. The Formula has more ports for air cooling. As well as one more port for Liquid Cooling. I assume that the differences are very small. I don't cool the VRMs (yet), but the rest. Everyone has to decide for themselves whether it makes sense. The 5950x runs very well on this board. You can find a comparison of the three boards here: https://www.bhphotovideo.com/c/compare/ASUS_Crosshair_VIII_Formula_vs_ASUS_Crosshair_VIII_Dark_Hero_vs_ASUS_Crosshair_VIII_Hero/BHitems/1487130-REG_1608601-REG_1487131-REG

Here are a few things to try out. 1. update bios 2. if you have m2 like me it is normal. (However, the latest update shows it). 3. you can bring up the carrier in windows. (Watch youtube, that works too) 4. try to insert the m2 in the 1st m2 slot on the mainboard that is the left one when you look at the board.

...which ?

Ich denke der hier: EKWB Velocity D-RGB Alternative wäre wenn man sich noch RGB wünscht: https://www.digitec.ch/de/s1/product/ekwb-ek-velocity-amd-rgb-nickel-acetal-cpu-wasserkuehler-12858950#gallery-open

So I bought the motherboard 1 day ago, didn't get a code for cashback.

No.