Xcode 6.1.3 can't change simulated screen size

Question

Using Xcode 6.3.1 I needed to simulate sizes to make the app compatible with older devices, I went to menu just to find that I can't select different screen sizes.

What am I missing?

EDIT

Another project, this time using size classes:

This option makes the entire storyboard use a specific screen size so I can see what is happening at design time

Maybe this is intended? To make people use size classes?

Answer 1

So, after some time (almost a year) I still haven't found a solution. The new preview is supposed to replace the old "Simulated Screen".

This is how you enable it:

And this is how you add any number of devices side-by-side:

The reason they added this is because you can now see many resolutions at the same time and see better what you build and how it will look in the various devices available.

I don't agree with that, I still miss the "Simulated Screen". I think it was a better solution, but they removed. We have to deal with it.

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Before this turns into a race to see who gets the bounty I'm going to close this.

@mcatach : Thats not the point. Xcode before 6.3.1 allowed you to see your storyboard in the interface builder with the device size you wanted. So we could use size classes and see in a particular resolution how it should look.

@aman.sood : This wont do. Changing the development target will not do anything to the interface builder, only remove size classes on older targets. Preview helps, but could be better. Using actual device is required to publish but it's not a solution to see different resolutions, that would mean you need at least 6 devices (7 with iPad mini).