Welcome to Ancestris!
To answer your questions:
1: You can see that from the Death column, if there is a date in there, the person is dead.
2: There is no official GEDCOM tag, to denote that. (GEDCOM is in capitals, officially)
Suggestion:
Look in the extensive English Help file
https://docs.ancestris.org/books/user-guide for the answer on a lot of questions.
In there is an explanation too, about how to add columns to the entities table and how to sort them.
Have fun with Ancestris.
Mother10