Can I Use a PCIe NVMe SSD in a PCIe Motherboard Slot?

Can I Use a PCIe NVMe SSD in a PCIe Motherboard Slot? can i use pcie 4 0 in 5 0 slot can support up to six PCIe expansion IO cards, as identified in Table 4-1 Slot 1: IO Card (8 gigabit or 16 Gb Fibre Channel ) PCIe Slot can you run ddr4 in a ddr5 slot While AMD made a PCI Express slot mandatory on X670 and even budget B650 motherboards, Intel's high-end Z790 chipset only brings Gen5 PCIe lanes

can you put ddr3 in a ddr4 slot PCIe Gen 5 is expected to deliver theoretical read speeds of 14,000MBps for NVMe SSDs, compared to the theoretical maximum of 8,000MBps on PCIe