DDR4 vs DDR5 RAM: What's different and which one should you buy?

Can you use DDR4 memory with DDR5 cpu intel? can you use ddr4 in ddr5 slot DDR4 is not compatible with any earlier type of random-access memory due to different signaling voltage and physical interface, besides other factors can i use m2 pcie 40 in 30 slot A memory adapter could allow you to use cheaper DDR4 memory in your DDR5 motherboard until prices come down for DDR5

candy bars slot check your manual but generally with two sticks A2B2 is what you should be using Exactly this, what if you bought a mobo with only 2 slots?