Closing ResultSet and Statements

["Antony Paul" <antonypaul24(at)hotmail(dot)com>]

Hi all,
(Sorry if repost. I posted it some days ago but couldn't  found on the list)
1. Is it necessary to close all ResultSet and Statements in PostgreSQL.
2. How to know that a ResultSet is open ?. Any views to query this
information?.
3. Do closing a Statement closes the ResultSet ?.
4. I saw an option of  autocommit = true in the postgresql.conf file. What
is its use. What is the default behaviour if it is commented. If I set this
to true do I have commit on all connections obtained without using a
connection pool ?.

rgds
Antony Paul