First off, this shouldn't been in this Forum, it should go
here
and secondly, I don't get your second question.
And third, for your first question, No mater what boss, in the advance tab, make sure Legace button is set to 'No'.
Then, create a new event and layer. Put the Star on the new Layer. And one the events window, make the event show the star. Now choose your boss. Click on the events tab in the NPC window and choose the "Death" and then click on your new event that shows the star. Then place your boss where you want.
If you want more help just ask!