BOK2GO your first point, I dont know why they do that, its dangerous though and I hope you kak on them when it happens.
Point 2 : its a good point, most if not all operators do this, I agree its wrong but sometimes ground frequency can be quite busy and if you are landing on 21L in JHB with 3 aircraft behind you with 5 mile separation between them and you turn off at T and just sit there you could cause all sorts of Chaos, but its obvious turning off at T that you are not going to conflict with other taxying aircraft, a different story at CT I suppose...good point I will advise future Captains (seeing as they do the taxi on the 737) of our taxi clearance in future
Point 3 : This also irritates the hell out of me when I hear it, I think its because flying over Africa with congestion and poor English being spoken you sometimes want to know that the station is listening to you before you do your whole speech only to get "Station calling say again", it seems to be normal over Africa and especially on the HF, I suppose its hard to break the habit when you cross the border sometimes.
Point 4 : Dont know what the difference is, at the company I work for there is no such thing as "fully ready"