Note that while Yorkshire and end feed fittings are both solder fittings, and both use capillary action to draw the solder into the joint, they are not the same as each other (since with the latter you need to feed your own solder in the end of the joint).
I wipe or brush flux run the outer surface of the pipe - but try not to get too much in it...
Yup pretty much.
Yorkshire is a branded product and hence probably more expensive than a generic solder ring fitting.
(end feed are cheaper still, and actually slightly faster to use IME since they have less mass and heat faster).