But rooting/jailbreaking (in WP world called "Interop unlock") has always been awkward and possible only for the most popular types of WP: Lumia, Samsung.
To write programs, it requires me to install Windows 8 or 10 — can't do with Windows 7 or Linux.
Even if I write a program, this phone requires special developer unlocking online for "sideloading" two apps maximum at a time, another arbitrary awkward limitation which can be circumvented by shuffling around with an SD card: loading an app into phone, moving the app to SD, disconnecting the SD, loading another app and so on.
WP8.1 does have an ability to install an app from a file directly, but only if it is signed with special enterprise signature, and that isn't cheap.
Of browsers, only IE and IE-based browsers exist for WP, and that means no proper customization and of course no ad blocking.
So the platform looked quite hostile to me and I wasn't motivated to explore any further.