Please help me on my below question?
Will HA work if I share NFS datastore across the cluster? Even though if works is it good practice?
We use this a lot. You do have to be concerned about whether or not your NFS server has enough capacity to handle a large recovery though. Don't use a low-end NetApp filer, add a shelf of SATA disks, and expect a hundreds VMs to come up very quickly.
It's very easy to create hotspots on NetApp filers if you de-dupe with ASIS and a boot storm can be ugly. The flash cards will help you with this too.