UI in corners of multiple screen sizes?

I'm trying to figure out the optimal layout size for my main platform iPad, but I also want it to work on iPhone.

iPhone 4: 960 × 640 (3:2 ratio)

iPhone 5: 1136 x 640 (16:9 ratio)

iPhone 6: 1334 x 750 (16:9 ratio)

iPad 2: 1024x768 (4:3 ratio) (also iPad mini)

iPad Air: 2048x1536 (4:3 ratio) (all retina ipads)

I'm working with 1024 x 768 in C2.

Is it possible to make a game that fills the entire screen on all devices, and at the same time shows game UI like score, buttons etc in all the four corners without letterboxing and black bars?

I've been reading https://www.scirra.com/tutorials/73/supporting-multiple-screen-sizes but didn't see anything about UI elements in the corners.

do everything as in the tutorial for the screen size i will only discuss the Hud , you have to add and anchor behavior to each element , tweak the behavior proprieties to make it in the position you want. , this a methode it may give your good resault , but another great and very precise methode , is to place Hud automaticly using the event-sheet , in start of layout make the object placement using set position , and the expression layout.tayout top layout.left layout left / right are usefull to know where to place the object

Ah thanks that's smart! Is it possible to lock the rotation on iOS devices, since in portrait mode, it would probably look very odd