Issue with cookie persistence

Yes I think it will. I think what you need to do is check for the presence of the Cookie and not insert it if it's already present or, better yet, apply the Cookie persistence via a profile, assign a default pool (2) and change your iRule to this;

when HTTP_REQUEST { 
 if { [string tolower [HTTP::path]] starts_with "/abcd" } { 
  pool Pool1 }
 else { 
  persist none }
}