A:AnswerYou probably wouldn't be able to flip the card and have it fit the slot and have the screw to secure the card in the right place. From what I've seen, most graphics cards are designed to have the fan facing down.
A:AnswerThe HP OMEN by HP Obelisk Desktop 875-0024 is upgradeable up to 32 gigabytes DDR4-2666. So, yes, you can add another 16 GB DDR4-2666 to this desktop.
A:AnswerHere are the memory upgrade specs:
Memory upgrade information
Dual channel (1 DIMM per channel) memory architecture
Two DDR4 UDIMM (288-pin) sockets
Supports PC4-21300 (DDR4-2666)
Supports 8 GB and 16 GB DDR4 UDIMMs
Supports up to 32 GB (unbuffered) on 64-bit computers.