ORACLE - RAC 10gR2/11gR2

How to delete CRS HOME ?
We have a automated way of cleaning up CRS as show below
1) Run rootdelete.sh script present in $ORA_CRS_HOME/install directory
2) Run rootdeinstall.sh script present in $ORA_CRS_HOME/install directory
3) Manually clean up the CRS :
1. Remove following files as root user on ALL NODES IN CLUSTER
rm /etc/oracle/*
rm -f /etc/init.d/init.cssd
rm -f /etc/init.d/init.crs
rm -f /etc/init.d/init.crsd
rm -f /etc/init.d/init.evmd
rm -f /etc/rc2.d/K96init.crs
rm -f /etc/rc2.d/S96init.crs
rm -f /etc/rc3.d/K96init.crs
rm -f /etc/rc3.d/S96init.crs
rm -f /etc/rc5.d/K96init.crs
rm -f /etc/rc5.d/S96init.crs
rm -Rf /etc/oracle/scls_scr
rm -f /etc/inittab.crs
cp /etc/inittab.orig /etc/inittab

2.If they are not already down then kill off EVM, CRS and CSS process as root user on ALL NODES
ps -ef | grep crs   
kill <crs pid>
ps -ef | grep evm
kill <evm pid>
ps -ef | grep css   
kill <css pid>

3.Remove the files in /var/tmp/.oracle or /tmp/.oracle on ALL NODES
rm -f /var/tmp/.oracle/*
or
rm -f /tmp/.oracle/*

4.Remove the ocr.loc at /etc/oracle on ALL NODES
5.De-install the CRS home in the Oracle Universal Installer
6.Remove the CRS install location on ALL NODES
In case you have not removed the CRS install directory, please do so.
7.Remove OCR and Voting disk from shared location from any 1 node

How to drop db and Home HOME ?
DROP Database  or Use DBCA:
shutdown abort;
startup mount exclusive restrict;
drop database;
exit

Use runInstaller to remove db and ASM home
Hope this helps !!