Can anyone help me?

[snowdust]

Hi There,
    I have a few question here. I am a newbie in dns stuff so please
forgive me if i do not know anything.
1)Is there any cache file in the BIND? Because last time my Sysadmin set
a hostname for me, but now since i change the hostname of the same
machine, the machine still resolve to the old address. When you nslookup
the new host, it resolved well. But when u nslookup the ip instead, it
resolved to the old hostname. I redo all the zones files but still in
vain.
2) May i know what number should i put in the serial under the zone
file? Is the format yy-date-serial?
3)My machine also canot do a reverse dns.. Can anyone help please?

Thanks!!
Trevor