Any resource can be used as an anonymous clone as it requires no additional support from the resource agent. Whether it makes sense to do so depends on your resource and its resource agent.

Globally unique clones do require some additional support in the resource agent. In particular, it must only respond with ${OCF_SUCCESS} if the node has that exact instance active. All other probes for instances of the clone should result in ${OCF_NOT_RUNNING}. Unless of course they are failed, in which case they should return one of the other OCF error codes.

Copies of a clone are identified by appending a colon and a numerical offset. Eg. apache:2

Resource agents can find out how many copies there are by examining the OCF_RESKEY_CRM_meta_clone_max environment variable and which copy it is by examining OCF_RESKEY_CRM_meta_clone.

You should not make any assumptions (based on OCF_RESKEY_CRM_meta_clone) about which copies are active. In particular, the list of active copies will not always be an unbroken sequence, nor always start at 0.