Hi @Ravi_S1
1st I agree with the previous user you should have upgrade to 7.17.x first and used the upgrade assistant. You can not really downgrade unless you can restore and start over. If you can that might be the best path...
A lot has changed in 8.x including restricting access to system indices that start with . like .kibana_xxx
You actually have to create a role that allows access to restricted indices if you want to operate on them see here I wrote a little post on that
All that said I am not sure of closing that index and restoring a past version is going to work... It seems you have no where to put that shard.