Backup file name
I use 12.5 and save the backups in version 11 files. Every full and incremental backup is stored in a separate file.
Is it possible to add the word "full" only to the full backup filename?
The files naming in legacy version of archive format is crucial for proper parsing of it, so it's not possible to adjust only specific file name in the chain. To determine the type of particular backup in the chain you should view it from web console interface from Backups tab: select archive -> "Show backups"
P.S. Overall it's not recommended to perform manual manipulations with the backup files outside of Acronis Backup interface.