Is it possible to develop an app only on specific device size? I now develop my iOS app which I initially wanted to develop on all the device sizes (4, 4.7, and 5.5-inch iPhone and also iPad), but later found that it is insanely painstaking, boring, and tough work to develop on all the sizes using Auto Layout and Size Classes, so I now consider developing only on 4.7-inch iPhone 6. 

However, while I can target the iPhone families only (selecting iPhone, not Universal, when starting a project), can I develop only on 4.7-inch iPhone?

If it is possible, how can I do? I want to know if it is possible and approved by Apple itself, or is possible but might be subject to the reject by Apple, or is not allowed by Apple. Any link to Apple documentation would be appreciated...
Hope this helps you.
As of May 1, all new iPhone apps and app updates submitted must support the 4-inch display on iPhone 5. All apps must include a launch image of the appropriate size. Learn more about iPhone 5 support by reviewing the iOS Human Interface Guidelines.
And as per App Store Review Guidelines

2.10
iPhone Apps must also run on iPad without modification, at iPhone resolution, and at 2X iPhone 3GS resolution..Please refer this

Else Apple may reject your app if app is not as per apple review guidelines