how to activate Debugging monodeveloper or visual studio editor in unity 5.4.2?

1. I am using unity 5.4.2f2 and upgraded a project developed in unity 5.0.2. when I run the project on unity 5.0.2, I can put breakpoints and can debug in monodeveloper properly. But when I run the same project in unity 5.4.2, the breakpoints does not get activated neither in monodevelop nor in visual studio. Hence can not debug through using breakpoints. The splash screen loads properly in scene view but no other screen gets loaded when button is clicked. But when I generate the apk, everything runs fine.
   

2. There is a huge difference in file size of android apk (around 47mb) and iOS .ipa (around 670mb) version which is very confusing. While 2.5 times bigger ipa filesize over apk filesize is considered normal, my case seems astronomically large. Am I missing something very seriously.

Advance gratification for any help on these regard.