How to make back button work properly

[Mew]

One annoying thing that I've noticed in Android (and it doesn't seem device soecific) is that the back button (the physical one, not the contextual one) is very inconsistent. For example, if I click on a link that opens youtube and I tap the back button, it takes me back to the browserbrowser, then that's correct.  However, some times when I click on a link, say newegg, and tap back, it brings me to the front page of the newegg app instead of the browser. Is there any way of fixing this cause it's super annoying and makes the point of a back button moot. 

 

Another thing. Is there any way of fixing SwiftKey's doubling of words and sometimes randomly going back and inserting words mid sentence. It drives me nuts.