At which OSI layer$($s$)$ does a router operate?

$80.$ Layers $1,2$ and $3,$ though it is normally regarded as a layer $3$ device because its specialist routing function is at layer $3.$

$81.$ Layers $1,2$ and $3,$ though it is normally regarded as a layer $2$ device because it is able to split up collision domains.

$82.$ Layers $1,2$ and $3,$ though it is normally regarded as a layer $1$ device because it is able to put signals on different types of medium.

$83.$ Layer $3$ because its function is routing, which occurs at layer $3.$ Other devices manage all the functions at other layers.

$84.$ Layer $4$ because routing depends mainly on port numbers.