When we build a universal application, Is that we should implement UI seperatey for iPod and IPad......?
Our app do not have orientation,splitting functionalities to develop......
Yes you should develop the UI seperately for ipod and ipad. For ipod create a folder ipod_content and place your .h and .m files there and same with the ipad. Same thing you need to do in Resources folder for separate xibs.
I depends. You can develop the UI so it scales accordingly and is usable on both iPod/iPhone and iPad unchanged (both via Interface Builder and via coding). But quite often you want to do things differently on the iPad since you've got a lot more space available. Unless you don't care about how it looks/feels like ;-)