HTTPS to HTTP redirection from three external web urls to internal web urls using F5 as a revers proxy

if in future we want to add internal server to load balance(for site1in.com) then how we will add the server and how F5 will decide to balance load (if any load balance method please confirm)

This is why you'd use a pool instead of a node. With a pool designation you can simply add members to the pool without modifying the iRule.

You also don't technically need the "-glob" option in the switch, since you're not searching for any wildcard values.