you can't pay upgd fee at the gate as KE doesn't do this.You can either use ur skypass miles at ckin counter under previous request or paying a difference to ur fare before checking in. as for upgd when overbooked they already know who to upgrade and that's usually ke customers(not even other skyteam platinum members) and you must have more than 40000 skymiles to be eligible to upgd.

As for F/class tkts they only sell 180....tkts (ke tkts) and they don't have any code share allotments.

Feel free to ask me anything you like about ke.