Translation:Is this your father?
This sentence is incorrect. Unless people are asking if objects are dads.... A better way of saying it would be Is he your father?
I think it's fine to use 这 for people meaning "this person", but I'm not a native speaker.
I think it's fine to use 这 for people, meaning "this person", but I'm not a native speaker.
Another weird statement. Nobody would ever say "This is your father" unless it was some sort of crazy long lost reunion.
This is a question (note the 吗 at the end of the sentence). And I think "Is this your father?" is a perfectly fine question to ask when, say, you're showing someone a picture of someone you think might be their father.