[Xposed General] Donphillipe:
Wow, this took all day but mainly due to my lack of experience, but I got it working. I re-ran the FlashFire with the "Mount /system read/write" checked and I waited 3 hours and the phone never went off the balloon intersected logo screen (ever loaded the "desktop" which I had seen after 8 minutes before with it unchecked). Then I finally decided to do a power-volumeUP reboot and the phone came back up. I checked XPosed again and I still had the error with SDK 21 not installed. Then I spent a lot of time researching and finally found a more modern version of Xposed Installer from here https://www.apkmirror.com/apk/rovo8...nstaller-3-1-1-android-apk-download/download/, which was 3.1.1. After uninstalling the back-level and re-installing this 3.1.1, then rebooting, all of a sudden XPosed Installer showed the big check mark saying it was installed and working. Then I made the mistake of downloading XPrivacy from the play store and then went through another iteration of XPosed not working, so I removed PlayStore XPrivacy, rebooted and finally got Xposed working again. Then at last I figured out to click the icons in the upper corners of XPosed for more options and went down the list to find XPrivacy and installed from there. XPrivacy still did not work but I finally rebooted and then went back to XPosed, clicked on the corner icons again and found it in the list, this time with a check-box option to enable and enabled it, then had to reboot again. Now XPrivacy threw up some splash screens I could not seem to clear and finally after tapping on the extreme edge of the display I got them all off to discover XPrivacy had installed with a list of apps to process. Now having used XPrivacy for 2 years only and old Android 4.0 system, I was very familiar with how it worked. I went in then with all the splash screens and finally tried to set it up to review ALL apps but clicking ALL did nothing. (Would have expected question marks by all apps???) I finally figured out, I had to go down the app list and manually check the pink box next to every App when then turned to a question mark in the box, rebooted and then XPrivacy started working for me in the old familiar way.

So for now, chalk up the mighty BLU Studio XL 6.0 D850Q as a win/win with a tedious but successful installation of root and then XPosed and finally XPrivacy and all without having a customized recovery ROM. And in fact if you do find yourself with one of these devices, use Kingroot, run it once (forced to install trial software, do it and remove later, Kingroot fails, run Kingroot again and it succeeds but do not open any of the Kingroot apps. Uninstall the trial software that Kingroot forced you to install with it, then follow this guide https://www.droidmen.com/remove-kingroot-kinguser-with-supersu/ (DO NOT try SuperSU-me or you will get a boot loop on this phone), now use the Terminal Emulator to run your SU and script to have SuperSU installed. Then run the FlashFire to install XPosed via this guide http://androiding.how/install-xposed-without-recovery-with-flashfire/, then install XPrivacy (if desired) from the corner icons of XPosed (not from Playstore)

Good luck!

20161201 - I'd try this first without the Mount /system read/write and report back which way works. Again the first time through I was using a back level version of XPosed Installer which still showed I needed SDK21 when in fact I may have not.

Also now I am challenged as I received notice of an OTA update just hours after flashing XPosed and it of course failed to update. Some say that FlashFire can add these and in most instances if you open FlashFire after you download the update (and before you install) that FlashFire should be able to automatically find the update and give installing it a go, however I am not that lucky. I plan to do more research and see if I can find where Lollipop stores these "Wireless Updates" as BLU calls them and at that point see if FlashFire can apply the fixes. If anyone has any insight, please let me know.

*Note 2: I have uploaded the factory flash of this phone to needrom.com in case you have a glitch. It is a clean flash with the IMEI and MAC staying the same.

** 20161203 - I did some searching with ES File Explorer and found the Update.zip so I decided to try to install it with FlashFire (it was the V28 update from Blu) and it soft bricked the phone. So I would say to anyone who plays out this same scenario, installing Root, the new XPosed using Flashfire, then XPrivacy from the new XPosed, then attempting to install any of the OTAs with Flashfire, to forget the last attempt. Attempting to apply an OTA after the final customization will cause the soft brick and you'll be like me now, starting all over with a fresh factory ROM to re-do your week's work. So I'll just plan to flash back to factory and leave up a few days until BLU gives me all the most recent updates and just reside myself to the fact that no more updates can be applied once I go Root/XPosed, or at least with the limited skills and understanding of Android that I have. Hope this helps someone else. (Of course it's real easy to get lost in all this, especially with XPrivacy now controlling FlashFire - you don't really know any more what is blocking what from executing and I suppose a soft brick was the number to bet on with all this underlying modification in place - anyway, I hope your mileage varies in a more positive way.)