4R: 4 revolute joints.
Spherical: Joint center lines intersect at a common point.
Angle between center lines of revolute joints:
for the orange input link is γ = 20 deg.
for the green output link is β = 90 deg.
for the blue link is α = 90 deg.
for the base link is δ = 70 deg.
The output link oscillates.
Oscillation period is 1 rev. of the orange input link.