1) Young's Double Slit experiment is an application of Two
Sources Interference. Young did it using light waves.
2) I don't understand what you mean by your question,
specifically the word approx. Heisenberg's Position-momentum
uncertainty is a law of physics.
In case you are thinking of uncertainty in Chapter 1 of Physics,
Measurements, there is no link. Chapter 1 talks about uncertainties
due to imperfections of human measuring equipments.
Uncertainty principle is about the fundamental law of physics,
and does not happen due to any inabilities of humans or any
measuring equipments at all. It is an extension of the
wave-particle duality, but exactly how is way out of the scope of A
level syllabus.