hi TS, sorry if i mis-quote u .
u must understand, there is no fixed rules.
terms like potrait lens etc are just, at best guides. more often, they confuse ppl.
"potrait lens" usually refer to mid tele, lens abt 100mm. these are good for half body shots. the focal length coupled w wide aperture, produce shallow depth of field.
but then, wide angle are very useful for potraits too. from group photos to showing the figure in relation to the background.
same for landsacpe. usually, ppl assciate wide angle 28/35 etc. however, lots of good landsacpe photos are made w tele lens too.
does that means one must have everything focal length to begin shooting?
of course not. in the field, photographers compromise, adapt, move to and fro, up and down to get the best view.