Splunk Enterprise version 7.1.0 and higher supports rolling upgrade so steps would be.
But when do we upgrade Deployment server before or after upgrade?
any recommendation for kvstore and app kv store.
Please share any challenges I might face during upgrade or any tips.
You can upgrade Deployment Server, Heavy Forwarders after LM, CM, IDXC, SHC upgrade. I'll highly recommend you to take KVStore backup before upgrade.