CVSup supfile question

[Alden Louis-Pierre]

    I just finished reading the Handbook for CVSup.  It appears to be a 
very simple process.  I'm currently running
FreeBSD 4.8 and from my understanding you can keep your sources up to 
date via CVSup.  Does this
mean if I were to do a fresh install of FreeBSD 4.8 and then CVSup my 
source all known security issues would
be resolved for the particular FreeBSD I'm running?  Would the following 
supfile update all of my sources for
FreeBSD 4.8?

    *default tag=RELENG_4_8
    *default host cvsup3.FreeBSD.org
    *default prefix=/usr
    *default base=/usr/local/etc/cvsup
    *default release=cvs delete use-rel-suffix compress
   
    src-all
 
    Is there a difference between using RELENG_4 vs RELENG_4_8?  I 
currently update all known security issues via
patch < /path/to/patch method and following the instructions for each 
security advisor. 

Thank You
Alden Louis-Pierre