Hello,

for the first part of your question: “ How to take full monthly backup in tape”:
You can create a GFS Tape Pool, this is a grandfather-father-son pool. In this you can define daily, weekly, monthly and yearly backups with retention settings for each of them.

https://helpcenter.veeam.com/docs/backup/vsphere/gfs_media_pools.html?ver=110

For the second part of your question: “and also tape are change the retation or identityfing its full backup.”

You can configure that tapes are exported after job completion. This is set in the backup job.
I did not use this export function up to now. In my understanding Veeam keeps track which backups are on which tape and it will notify you which tape to check into the library for a restore if you try to access data which reside on a exported tape.

Here you can find all information:

https://helpcenter.veeam.com/docs/backup/vsphere/tape_data_retention.html?ver=110

https://helpcenter.veeam.com/docs/backup/vsphere/creating_gfs_tape_jobs.html?ver=110

https://helpcenter.veeam.com/docs/backup/hyperv/gfs_to_tape_hiw.html?ver=110

:)