select * from sys.availability_groups;
giving zero rows selected. 

group_id    name    resource_id    resource_group_id    failure_condition_level    health_check_timeout    automated_backup_preference    automated_backup_preference_desc    version    basic_features    dtc_support    db_failover    is_distributed

drop availability giving as it does not exist..

DROP AVAILABILITY GROUP "OST-MOD-DBS-AG1";
Msg 15151, Level 16,...