what is a pcie x1 slot good for?

Can PCI-E 1x go into a PCI-E 4x slot? - can you put pcie 1x in 16x slot I've never tested it, but allegedly it will split a single x16 slot into an x8 x4 and x4 in can i put pcie x4 in x16 slot +1 Also cards must support being inserted into a smaller slot than they're designed for Some slots

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