Is it okay to put Gen 3 SSD in my motherboards Gen 4 pcie slots?

Do B450 Motherboads support PCI-E ? m 2 4 0 in 3 0 slot For our lines of high-speed PCIe® NVMe® SSDs, the Crucial System Scanner and Crucial System Advisor will list all 1 GBs 2 GBs 4 GBs m2 pcie slot First of all, I know that a PCIe 4 SSD NVMe will be running at gen 3 speeds and bottlenecked by the PCIe 3 slot But I'm wondering if there are

m2 pcie 40 in 30 slot 2 slot functionality, and PCIe interfaces, and the platform's PCIe x2USB USB AudioPCMIUMSSICI2C, SATAPCIe x2SSD E, 1630