Yes, Dialogue should be like a conversation. It needs pauses and punctuation, so in each time the speaker changes you start a new line and indent.
Yes, you indent each new paragraph.
They talk to each other.
Speak to each other
In a film, dialog is the collection of spoken words that the actors say to each other.
speak with each other
commas
commas
The chromatids are first separated from each other during the anaphase stage of meiosis.
The north and the south hemisphere are separated by the equator!
nothing
You are two people who are married to each other who are separated.
They can separated just by space, but also by a vertical line.