Yes, a starter motor from a 1.6 will fit a 1.8 and vice versa.
speed sensor is behind starter motor
Need more detail... Which mk1 and which mk2? (Year/Engine/Spec/Box type, ie '83 1.8 GTI, Manual) Depends on gearbox fitted to either.
starter relay location
yes they will
You need to modify the mk4 steering wheel to fit. Get the 3.5 cabrio wheel. It looks similar and no mods required
In the space under the hood.
Under the manifold on the Right hand side............
With adapters yes. Stock no. buy addapters and you can get them to fit.
yes I belive so
plug it
golf gti
Most if not all 4 cylinder VAG engines will fit in a mk2 Golf. However it will be much cheaper to buy a GTI rather than convert a non-GTI model once you factor in ancillary items such as GTI-spec front brakes, rear discs, a change of wiring loom, etc.