You need to read the CA-7 Systems Programmer Guide
in detail, particularly chapter 7 talking about backup and recovery, where this point is made:
The safest procedure to adopt is frequent backups of most CA-7 data sets and all systems under the control of CA-7. This includes all JCL, load module and control statement data sets, and so forth. All should be backed up on the same time period. During the backup of the CA-7 database, CA-7 should be shut down for totally predictable results.
Based on what I know about CA-7 (and I am knowledgeable but not an expert on CA-7), the answers to your questions are:
a) stop the queues during the backup, not the restore
b) it appears to depend upon why, exactly, you're doing the restore
c) are you starting CA-7 COLD or WARM? A CA-7 COLD start (there's at least 3 different parameters that force a COLD start to CA-7) means no data is retained about the jobs and queues previously. And that, in turn, goes back to your question (b) -- WHY are you doing the restore?