Per the help centre questions relating to development of Windows Phone apps are generally off-topic here, and should instead be asked on Stack Overflow (as you have).
There is a connection between the sites, both in terms of software, ownership, but also functionally, with moderators (and staff) having the ability to migrate questions to a more relevant ...
The fourth option, with the "browse for any site" option is only available to moderators (and employees of Stack Exchange), whilst the first, and the migrate to meta on the fourth are available to the wider community.
To get sites added to the list of sites on the fourth option requires the site to be out of beta, and also requires proof that there is ...
Currently the maximum width of images is 630px (all.css → .post-text img rule). With a 15:9 aspect ratio this gives a height of 1050px; at 16:9 it's 1120px.
Assuming SE allows this level of customisation for the individual sites, the simplest solution would be to simply decrease the default max-width of images. 400px seems to be a reasonable compromose ...
An official Android version has recently been released http://blog.stackoverflow.com/2014/01/stack-exchange-for-android-is-here/. An iOS version is in the works, but unfortunately no word on a Windows Phone version.
Your enthusiasm is commendable, but
This looks like a healthy Stack Exchange site
No it doesn't. 2 questions have been asked so far. This is not surprising since Windows Phone has been discontinued since 2017. I'm actually surprised it hasn't been shut down yet.
Also, Stack Exchange sites only get a logo as part of their custom design, and there's quite a ...
The answer is Yes. And here is one you can use. Not officially created nor has a title of StackExchange but it does possesses all the features you'll need. I'm using it and very happy with that. Please have a look.
This is by design. Compared to their respective main site, meta sites are generally low-traffic, and there's less of a need to have all posts conform to a certain standard of grammar, formatting and overall presentation. Any glaring problems can be pointed out in comments or addressed by moderators or high-rep users, so adding suggested edits would do little ...
There is one app, still not an official app, but it has a very good user interface, designed using the Windows 10 design language. Its called Stackie
All StackExchange sites are available. Scroll down the Pin a Site modal to reveal and pin your favorite Stack Sites.
I know that this is a WP [meta] site, but there is now a SE iOS app. Yesterday, on a whim, I had the same question, as the OP, myself and searched the AppStore. To my surprise I found one. I downloaded it, and it is very good.