What is the difference between border-radius 50% and 100%?
100% rounds 100% of each edge, 50% only 50% of each edge. If the corner is to be rounded by a radius that is too large for any given edge, then the effective radius will be smaller.
Can CSS outline have a radius?
The outline-radius property is used to specify the radius of an outline. It is used to give rounded corners to outlines. This property can only be used in Firefox2-87 (till march 2021) and from Firefox 88, outline-property follows the shape created by border-radius automatically, so this property is no longer needed.