Cut mesh into two objects along selected edge I want to cut the mesh along the blue line,I've tried different ways, with no luck

If I select the 4 edges then press P, then I get a Square shape rather than a mesh, I saw tutorial says edge split in Edge Menu can do the job, but I'm using blender 2.9 there is no such item in the Edge Menu, I dont want to use a plane cut either cause the mesh I'm cutting is a rare case that the edges forms a plane, I want a more universal way of doing this in case of the edges does not falls into a plane.
No worries, the split option is still there :)

Select your edge
Go Mesh &gt; Split &gt; Faces By Edges
Done.