Its only from Manhattan to Staten Island right ?

And from Staten island to Manhattan. But if you re asking about further destinations, then no. The ferry has only one track : Manhatten - Staten Island

No both ways

If I get your question right, you are asking for your way there... Take the R train to stop at Whitehall / south ferry. You will cross with a ferry, that is free. You will not need to pay to and fro. The same R train you will take back to Manhattan to connect.

Yes

And back....with Lady Liberty photo opp.