iOS Development: How can I build a complex structured iPad Application?

I have a scenario with 3 sub-applications embedded into a main one. I'm trying to use the splitviewcontroller to change my detailview's content, but I couldn't replace the detailviewcontroller without losing the popover.

Questions: 1-How can I build a organized structure to maintain my project? 2-How can I replace my detailviews viewcontroller by another? 3-Should I use storyboard or separated XIB's? 4-Can I "call" a splitviewcontroller from a simple view? (Login(single)->AppSelection(single)->App1(splitview).

Here is a sketch of my project enter image description here

Solution

Looks like you've already got it mostly storyboarded, so I would definitely recommend that approach!

I wasn't able to figure out how to segue to a split view using just storyboards and nothing else. You will have to get the button press and replace the window's rootViewController with your split view (which you could load from a storyboard, or just a plain nib, if you wanted.)