title: Develop a windows store app for Windows 8 and Windows 8.1
body: <p>is it possible to develop an app for windows 8 and it will run on windows 8.1 normally? what about the validation in the store? and its visibility in the store for users who have windows 8.1 on their pcs?</p>
  
  <p>why visual studio 2013 professional version is supported by windows 8 and not visual studio 2013 express edition for windows?</p>
  
  <p>if we developp a library in windows phone 8, could we reuse it in Windows 8.1 application? (specifically its validation in the store?)
  thx for ur answers</p>