There were some flaws in the TK app (maybe also on the website) last year where you were able to change destination also to outside the original region during invol. rebooking but I believe it has been fixed by now. Also I don't recognise the extreme possibilities available but it might be due to my ticket being an TK award and the backpacker/poster was on a revenue ticket apparently. But to me it sounds a bit too good to be true and it is def. not in line with the official TK invol. rebooking policy. I can almost guarantee you that you will receive a big "No" if you call TK CS and try to change destination from Africa to Australia. Official TK policy is that change of region is not allowed.