The StackOverflow app you are looking for on Windows 10 and Windows 10 Mobile. It’s a native app on Windows unlike a wrapper on StackOverflow website. The design is modern. It’s slick & fast.
Note: This is an unofficial StackOverflow app.

• Login with your StackExchange user id.
• View Questions, Answers, Comments
• Add comments, answers, upvote, downvote ( if you have logged in )
• Search Users
• View questions based on tag.
• Read inbox.
What you can’t do:
• Ask a question ( Coming soon )
• Can’t logout once logged in. Not documented in StackExchange. This is planned to be released as an update.
• Users can only login through StackExchange account.