Firstly, I'd like to point out it's recommended to have the SHC Deployer be on it's own.
Secondly, I will assume you have a Search Head Cluster and Index Cluster since you mentioned master node and deployer. You will have 72 hours until search is disabled due to the License Master not being available. If you expect the LM will be down longer than your 48 hours, I would first migrate the License Master role to a new standalone (or at least another machine) if possible.
https://docs.splunk.com/Documentation/Splunk/7.3.2/Admin/Aboutlicenseviolations
Yes, it is sufficient to stop the Splunk service on the instance. The cluster will be at risk if you lose a search peer (Indexer) however everything will continue to function without the Cluster Master, SHC Deployer, and the License Master (up to 72 hours).
Yes, indexing will continue as long as the replication and search factors are being met, even after missing the License Master for more than 72 hours.
Indexing does not stop, so regarding other files to backup, it's a good idea to always backup /opt/splunk/etc/ (recursive) on every Splunk server in your deployment on a regular basis. Regarding specific files, I would make sure you have your .lic license file handy to being able to switch LMs if needed, and the SHC Deployer you would want a backup of everything under /opt/splunk/etc/shcluster/ (recursive).
Not sure what 'everything' entails, but assuming the server is alive and well and effectively the same as it was prior to stopping Splunk (new version of Splunk is fine), then yes you can start Splunk on that machine and be running fine again. The Indexers will continue sending heartbeats and will detect when the Cluster Master is back up. The CM will do its thing, making sure the cluster is healthy and do bucket fixup as needed.
https://docs.splunk.com/Documentation/Splunk/7.3.2/Indexer/Whathappenswhenamasternodegoesdown
Good luck!
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