First of all, thank you for the sponsorship!!! I really do appreciate the ability of SBI to pull posts out of the dust level.

As for your questions.
ONE. and TWO. actually get the same answer from me.
To me, the switch you described is a failed solution from the beginning. There is almost always another way! If you have time to flip a switch, you are also likely to have time to push the people out of the way or throw something in the way of the trolley car to stop it or slow it down to give the others the time needed to escape.

I am glad to not have to be in the position to decide who lives and who dies... you try your best to save them all... even if it kills you in the process.

THREE. Your bad guy might be a good thing to throw in the way to stop or slow the trolley, but the prevents any chance of redemption on the part of the bad guy. I'm again thankful that I'm not the chosen executioner of this world! I would sacrifice myself, I'm fairly sure - even if accidentally - but I wouldn't sacrifice anyone else in my stead.

FOUR. and FIVE. - we're talking about majorly advanced Artificial Intelligence - but it's designed by a corporation for whom bottom line is more important than almost anything else... So, no, I wouldn't buy either model - nor accept one as a gift. We already know what happens when bots get out of control here... (I'm probably going to be helping the people looking for ways of outwitting the AI, in your scenario.)

(Speaking of clever AI... or clever Markdown box... so, renumbered the questions.)