There are lots of ways to kill Ad Avis at the end of Qfg 2 yup

And it all depends on what actions your character takes and what class he is

From the looks of it your character is originally a Wizard but you bought the magic rope from Keapon Laffin's magic shop so you trickered the Thief's ending sequence in which the Hero (since he obviously bought the magic rope) follows Mayzun's vail into the palace Harem and from there he has to sneak past the Evnough guards and then cross the balcony with the magic rope and up to the tower where Ad Avis is standing. Then he gets to throw daggers to Ad Avis in order to kill him. Of course that's the normal way for a thief to handle the situation

But there are lots of alternatives (for example replace daggers with mud

)
Now what happens with Qfg 3's intro.....
It's really simple actually. The Qfg 3 makers estimated how the ending sequence of Qfg2 should normally be and the most likely way that each Hero according to his class (Fighter - Magician - Thief) choose to handle the situation. So once the games knows which class your Hero belongs to - it will show you the most likely and apropriate way things happened when you killed Ad Avis in Shapeir in order to tie that event with the current situation in Tarna

If you try and experimate with this and choose another class of a Hero to play with you will see that the intro versions will vary accordingly

Sure you did solve Qfg2's ending as the Thief class Hero would (and it's not wrong since it worked after all! ) but the most apropriate way for your Wizard Hero to solve the pazzle (or any other class you would choose for the matter) is the one they show in Qfg 3's intro