Hello,
Talking about the Thales FMGC.
1:Yes
2:Yes
3: I heard that story too. Some colleagues told me it happened in the past. But I don't understand how technically it's possible. For the FMGC to switch from ''Approach phase'' to ''Done'' the condition is that the aircraft must be on the ground for 30 seconds. FCOM- Aircraft Systems- Auto Flight- Flight Management- Flight Planning- Vertical Functions
For the Tips in general, I recommend you download the '' Thales New FM Pilot guide book'' available for free on Smartcockpit. You have extra information about the FMGC that you won't find in the FCOM.
Cheers.