Yes you can directly upgrade form 10.2.0.1 to 10.2.0.5.
Same counts for clusterware as RDBMS. Only difference is clusterware would be able to do this in rolling fashion (one node after the other), while RDBMS upgrade requires a downtime.
- Download 10.2.0.5 sw and unzip
- Stop crs - $CRS_HOME/bin/crsctl stop crs.
- Run preupdate.sh available in installation files
- Run runInstall
- Specify correct Home
- Select node
- Run prerequisite checks and run installation
- Than run upgrade script as root
To check version run:
$CRS_HOME/bin/crsctl query crs activeversion
$CRS_HOME/bin/crsctl query crs softwareversion