What is the minimum requirement for reading megillah? Can one simply read it without trope? The reader would be reading from a kosher megillah. Thanks!
Yes, reading without trope works. Getting the grammar/pronunciation right is critical. Although you don’t need trop, you need to stop in the right places. Basically where there is an etnachata or sof pasuk. Basically, don’t do something like:
.ויהי. בימי אחשורוש הוא. אחשורוש המלך מהדו ועד־כוש שבע ועשרים. ומאה מדינה
You get the idea.
Can you write in the megillah a period?
Yes, but do it in pencil. Also commas, semicolons (for etnachta) if you want. You can write all the vowels, but that is laborious. The source for this is Shulchan Arukh OH 691:9, and in the commentators there, who say having the trop written inside is better than reading without trop. Also, writing it in pencil makes it not really permanent and not part of the megillah.