It's something we all think about at some point or other - whatever version/branch/ring of Windows 10 Mobile that you're currently on, and especially if it involves Insider builds or trying loads of applications, there will come a point when you fancy 'factory fresh' performance again. No under-the-hood cruft, no detritus. Here are the steps needed to keep things smooth and ensure that you don't lose much in the process.
NB. This procedure doesn't necessarily apply to anyone going back from an Insiders build to 'production' status, i.e. using the (Win32) Device Recovery Tool (DRT). You can grab this for yourself here if you don't already have it on your Windows 7, 8 or 10 system. The problem is that the backups made using modern (AU, CU, FCU) Insiders builds aren't fully compatible with the production firmware images on Microsoft's servers, in some cases from the 'Threshold' days. If you do want to go back to full production status and you do try restoring immediately from a modern backup then you'll end up with a phone with no Start screen! It's a known issue and just one of the gotchas of being on the Insiders programme and wanting to hop backwards and forwards. There's a workaround, of course, and I step through it here in an old tutorial. (Quick preview: opt out of the Insiders rings, use the DRT to go back to 'production' Threshold or even back to 8.1 in some cases, don't restore a backup, head straight for the production Anniversary Update, then hard reset once that's in place and only then opt to restore your original backup!)
So - you have a Windows 10 Mobile phone and it's got messed up with your own fiddling, with app installs, with previous Insider builds - whatever, something important is not working right and you feel that a refresh is in order under the hood - here are the steps needed.
0. Plug in!
Yes, there's a step zero - it's kind of obvious but I'll state it anyway. Don't try any of this with a low battery. Charge your phone before you start and/or, for belt and braces, keep it plugged into the charger as much as possible.
1. Export your podcast feeds
Go into your chosen podcatcher and clear its storage/cache of MP3s (since you don't want these to be needlessly backed up - they can always be downloaded again afterwards if needed). Now the important bit - make sure that feeds and/or database are backed up - this usually happens to OneDrive, but you may have to upload a file or two manually (e.g. in the ubiquitous OPML format) - depends on the app (Grover Pro is shown below).
2. Back up
Check you do have a full backup: go into Settings/Update & Security/Backup, and make sure both check boxes are on ('Back up content', 'back up settings'). Now tap on 'More options' and wait a few seconds while the information is retrieved from OneDrive. Check that 'Last backup' time and date is recent (e.g. within last 24 hours).
Also, check that backup is toggled on for all installed applications (see screenshot below) and perhaps consider doing an extra 'Back up now' (and then wait!!!)
3. Finish your games
You'll lose game states in most cases, so finish off that tricky title and draw a line under it before moving on?
4. Check you know your passwords
The usual precautions about double-checking that you have any relevant passwords (e.g. Microsoft, Google, Dropbox) to hand, to save messing around with recovery emails later! I use an encrypted database system with its 'blob' on OneDrive and Google Drive, accessed using this, for example, but your mileage will probably vary here.
5. Save your Start screen layout
A bit of a 'belt and braces' hack, this, but just in case the auto-restore of this doesn't happen(!), screenshot your current preferred Start screen layout (power+volume-up button), repeat for each screen's worth! Upload the resulting images to OneDrive or share them with yourself via email etc.
Or, of course, you might choose a 'Spring Clean' approach and welcome the chance to create a new layout, with the apps and shortcuts that you currently now use?
6. Photos, PIM up to date?
Make sure that all of your latest photos are synced up to Microsoft Photos by going into this and hitting the 'refresh' control. You don't want to risk losing a valuable recent photo!
Ditto for Outlook Mail and Calendar, do a final sync to make sure any latest phone tweaks to PIM apps are synced up to the cloud.
7. Take out your SIM if you're expecting a call
Take out your SIM card and put it in another (old?) phone for the time being, if you're worried about not being contactable for a few tens of minutes.
8. Reset time
Head into Settings/System/About and swipe to the 'Reset your phone' button. Tap this and confirm, to set the phone erasing itself - this will take several minutes, so be patient.
9. Signing in
You'll be faced with a smartphone that's showing the typical set-up screens: choosing country; accepting Microsoft's EULA; setting the date and time; selecting a Wi-fi network; agreeing to go 'Express' with default settings. You'll be familiar with all of these and it's not rocket science to work through
Next is being given the chance to 'Sign in' and you'll almost certainly want to do this. Give the phone your Microsoft account email and password and tap 'Next' to get the OS looking in your account's online (hidden) backup area. The right and most recent backup will hopefully be highlighted, but do double-check it. You may also be asked to complete two step verification by one of your chosen backup methods (e.g. code sent by SMS to your nominated phone number).
10. Restoring your settings and data
You're now faced by a number of restoration steps. The first involves a progress bar and should take about ten minutes - you will also be asked to confirm your details again at around the 20% mark, for extra security.
Next, step through the agreements for OneDrive and Cortana. Windows 10 Mobile then helpfully gives some hints along the lines of being patient in terms of the app installs. Which proves to be apt advice - you may think you're nearly there but in fact you've still got at least an hour of background application installs to (lightly) supervise.
11. Re-installing and updating applications
Head into the Store and look on the menu for 'Downloads and Updates' - hit this and then scroll through the long list of updates waiting until you come to the Store itself. Tap on its download icon and update this first, for a smoother ride overall! The Store will update and then relaunch itself. Go again into 'Downloads and Updates' - tap again on 'Check for updates' (or 'Get updates', depending on OS branch) if need be, and you should see around 40 or more updates waiting:
At this point it's safe to simply tap on 'Update all' and then go off and do something else for an hour or so. True, you could insert your SIM at this point and use the phone for the basics, but I'd advise against it - your phone needs to be on Wi-fi and relatively undisturbed - it's doing a lot of installation work and will be slow and (probably) hot during this phase. So best leave it alone to get on with it.
12. Final checks
Once everything's installed and settled down, power down and insert your main SIM, then run through the basic applications to make sure that your PIM data syncs all happened OK. So that's Outlook Mail and Calendar - is everything restored/synced and in place? Use the 'Refresh' tool in each if not.
Then it's into Photos, usually, and give that a few minutes to sync down a decent number of thumbnails from your online library. And you'll want to head into your podcatcher too, importing all your shows/feeds from wherever you saved your exported list above.
Phew!
Don't be too disheartened by how many steps I've broken all this down with - although the various steps take quite a bit of real time while data shuttles backwards and forwards, there's not much for you to do and there's nothing too tricky.
Comments welcome if you feel the need to try all this - how much slicker does Windows 10 Mobile seem now? How much of a difference did the refresh make?