10.2.0.4/10.2.0.5 Hot Backups (11r2 considered too) - ORACLE_HOME

Question

Scenario:
We have a script that runs a hot backup of each database on a VM server. Because there are multiple databases on the VM we have a mixture of database versions. For example, we might have 8 databases on Server A running 10.2.0.5 and we might have 2 databases on the same server (Server A) running 10.2.0.4 (different homes of course). Our hot backup script sets one single ORACLE_HOME env variable for running a hot backup for all databases.
Question:
Can I safely export the script's ORACLE_HOME as 10.2.0.5 for all the databases on the VM and still get successful hot backups of the 10.2.0.4 and the 10.2.0.5 databases?
Followup Question:
When we eventually start upgrading the 10.2.0.5 databases to 11r2, will a single ORACLE_HOME set by the same hot backup script work knowing that some databases may be 11r2 and some may be 10.2.0.5 on the same VM?
Thanks for your input.

Answer 1

The cron job runs a script that builds a script that selects the SIDs on that server and then it runs another script that builds a sqlplus script (script detailed below). The sqlplus script is a file that contains the following commands for each SID on the machine:
set feedback off
set pagesize 0
set termout off
spool /xxx/xxx/b_backup.sql
select 'set termout on' from dual;
select 'set echo on' from dual;
select distinct 'alter tablespace '||tablespace_name||' begin backup;'
from dba_data_files;
select 'select from v$backup;' from dual;*
select 'exit' from dual;
spool off
*@/xxx/xxx/b_backup.sql*
exit
So what we end up with is a sqlplus file that will execute the above commands for each SID on the box. The databases may be different versions though (a mix of 10.2.0.4 and 10.2.0.5).
My basic question is: Will using ORACLE_HOME pointing to 10.2.0.5 sqlplus have any negative effect on backing up a 10.2.0.4 database?
My secondary/follow-up question is concerning future upgrades to 11r2: Will using ORACLE_HOME pointing to 11.2.0.2 sqlplus have any negative effect on backing up the remaining (not yet upgraded) 10.2.0.5 databases?
Does sqlplus version matter when running sqlplus from a different ORACLE_HOME on a database with a different version?