dataguard switchover/failover

I have 24x7 application running on production database. database size in TB.my goal is to migrate that application on different server and once application will be runing on
new server (standby db) , i will delete primary db on old server.To miminze outage,
i had created physical standby db on new server. Both primary and standby db are in synchronization and archived logs are shipping from primary
to standby with NO DELAY. Also, Standby redologs had created on primary database. I need to choose between switchover or failover.

if i choose switchover, than application will run on standby database considering as primary. and primary will become standby.
1) Can i remove old primary from the dataguard configuration once it become standby after application migrate on new server wihout any downtime?
2) if yes, how to delete old primary from existing configuration?

if i choose failover, application will run on standby db as primary db and primary will nolonger exist.
1) in this case, something goes bad after one hour or sometime, how to rebuild my old primary with no data loss. What is backup plan to rebuild it?
2) I have no data gaurd broker in my environment. Can you tell me step using SQL command to do failover? I searched on metalink but couldn't found. they all mentioned failover with DG broker.

Thank you.