Why don't you just have abc.xyz.com and abc12.xyz.com DNS addresses resolve to different IP addresses so they hit separate VS on the BIG-IP, therefore allowing you to do the different things you're looking for.
Either that, or you need to have an iRule that selects a different pool and also disables serverside SSL. Something like:
when HTTP_REQUEST {
if { [HTTP::host] eq "abc12.xyz.com" } {
pool
SSL::disable serverside
}
}
But separating to two separate VS is the easiest thing to do, unless you have a certificate that has the multiple hostnames in it (SAN or wildcard).