I did not get your first question, please be more specific. Regarding support for GPT: Symantec is looking into it as an enhancement for next major BESR release, right now BESR 7.x does not support GPT.
If the backup job was interrupted, it cannot automatically be restarted. The backup job will launch again on the next scheduled time. Depending on the type of interruption, this could cause a corrupted image file. Backup Exec System Recovery should detect this and create a correct incremental or baseline.