Through other software I managed to obtain a spline with length of 200mm.

The points would be these:

pts = {{0, 0}, {45, 10}, {75, -15}, {130, -20}, {180, -33.25904718}}

The last value in Y (-33.25904718) is not accurate for this directly depends on the length of the spline, that is 200.

1. I get this value in the SolidWorks software, but how can I get this value using Mathematica?

And another question:

2. There is only one solution or there may be several other?