Does DDR3DDR2 RAM Work on DDR4 Motherboard?

How to tell what kind of RAM you have can you use ddr3 in ddr4 slot Memory For Desktop and Laptop DDr3, DDr4 PHP can i put a pcie 40 in a 30 slot Completely impossible Even if motherboard has both types of DIMM slots only one of them can be used at a time #2

can you put a pcie x4 in a x16 slot DDR5 has about the same latency as DDR4 and DDR3 DDR5 octuples the maximum DIMM capacity from 64 GB to 512 GB DDR5 also