How do I create lines for all points on the layer where the same radian and same length of line are representated on all points regardless of the point locations?
All you need to achieve what you're looking for is the Geometry by expression tool. Expression:
This should draw a line 4000km long, if your layer units are meters, at 270° from North. The
project function throws a point a certain length away from your original point in a certain direction in radians.
Bear in mind that such long lines will have radically different shapes on different map projections. If you're looking for a loxodrome, you should be working in a conformal projection.
There might also be problems if your line crosses the limits of a projection so you will need to take that into account.