You play the ace and East drops the jack.
Correct play: Lead from South hand and finesse 9. You will need to return to the South hand a second time and finesse the 10.
If you don't have 2 more entries to the South hand, you might as well play the king.
2.
North South
AKQ9 xxx
You play the ace and both follow. You play the king and East plays the 10.
Correct play: Lead from South hand and finesse 9.
3.
North South
AKQ8 xxx
You play the ace and East follows with the 9. You play the king and East follows with the 10.
Correct play: Lead from South hand and finesse the 8.
The following situation is NOT a restricted choice situation. It looks like one, but it isn't. I wrongly thought it was and lost a cold slam. :-((((
North South
AKQ9xx xx
You play the ace and East follows with the 10.
Correct play: Play the king. Since East can false card with J10x, this is not a restricted choice situation.