I had Lumia 630 on W10 since .107 and now I reset it via WDRT and it is 8.1 again, how do I update it to W10 again via Insider to 10586.494, what program do I choose, because nothing is showing up.
You can't update your phone because it does not support Windows 10 Mobile upgrade. The last build you could get through insider app is .107, but if it won't work for you now it means MS has blocked that too.
Only the Microsoft-built Facebook app works with Windows Phone 8.1.
The Facebook Messenger App is built by Facebook Inc for both Windows Phone 8.1 and Windows 10 Mobile; however, the WP8.1 version is substantially different, adhering to Modern UI design guidelines.