URL redirection with retaining the original on browsers

You can accomplish this with Rewrite Profile: https://support.f5.com/kb/en-us/products/big-ip_ltm/manuals/product/ltm-implementations-11-5-1/23.html?sr=51290275

You could also point the DNS records for www.test.com to abc.com and simply use the same pool for abc.com as the pool for test.com. This will also require the web servers to be configured with a name virtual host (apache terminology) for test.com which uses the same web root as abc.com.

Are trying to convert the links inside the HTTP response from www.abc.test.com to www.test.com again?

You can create a new stream profile to translate the domain names or use an iRule like this:

when HTTP_REQUEST {
   set to_change 0
      if { [HTTP::path] contains "/urltomonitor" } {
         set to_change 1
   }
   STREAM::disable
}

when HTTP_RESPONSE {
   if { $to_change == 1} {
      set original "http://www.abc.test.com"
      set replacement "http://www.test.com"
      STREAM::expression "@$original@$replacement@"
      STREAM::enable
   }
}

You will need to modify the [HTTP::path] to match your url that contains redirection, and you still need to attach "stream" profile to your virtual server.

"user would try to access www.test.com but it needs to be redirected to www.test.abc.com"

The elephant in the room is whether you actually own test.com.

After that, you don't need rewrites or redirection, you simply need to point the DNS record to the same IP as www.test.abc.com and tell the web servers that serve www.test.abc.com to serve the same page(s) when the HTTP "Host:" header contains www.test.com.

Of course if your webpages contain hard links (rather than relative ones) you'll need to do some STREAM changes to alter URLs-on-the-fly, per the post from Minn.