Question 1: How to create standby database primary database backup .
Answer : Starting of 11gR2, without having Primary backup RMAN duplicate can create standby database over network via oracle database services.
Ex. If we check the log , you will below logs
Starting restore at 21-JAN-24
using channel ORA_AUX_DISK_1
channel ORA_AUX_DISK_1: starting datafile backup set restore
channel ORA_AUX_DISK_1: using network backup set from service CDB_PR
channel ORA_AUX_DISK_1: specifying datafile(s) to restore from backup set
channel ORA_AUX_DISK_1: restoring datafile 00001 to /oradata/CDB/data01/CDB/datafile/o1_mf_system_ltrj6j0p_.dbf
channel ORA_AUX_DISK_1: restore complete, elapsed time: 00:00:45