[Windows Phone 8 General] lmiked:
Hello everyone, based on the replys I've seen on this thread, I believe this one will help everyone, but it will definitely help Lumia 1520 Owners (like me)!!!

So, I've been experimenting many times with installing the Win10 TP over the last couple of days, I was able to install both Slow update version and Fast update version... I've also tried flashing with different FW versions before doing the hacks to get the Win10 TP builds, and came to the conclusion that no matter what hack/registry modifications you apply, on some FW versions you simply won't get any builds found, I believe it is due to some region or version check the windows insider app does, that is not present on the about page, so we don't know where that registry is, and it would be extremely difficult to find and change it in order to pass the checks... Anyway, I know for sure that this FW version I'm using works and allows us to change the needed registry values, and does pass whatever checks other FW versions, for it's the one I'm using, and I've been able to install Win10 TP, reflash the firmware back to WP8.1 Denim, and then again repeat the hack and install Win10 TP multiple times, so, here is a mini tutorial based on the original one on this thread, bare in mind that this will WORK for RM-937 Lumia 1520, and it will probably work for other models, but you need to find the right FW version/product code that will be similar to the one I'm using on the Lumia 1520, I recommend trying DENIM from APAC (Asian Pacific) regions, which is the one that worked for me.

So, follow these steps carefully:

1. Download Firmware update with this product code 059V3T3 it should be version 02540.00019.14484.37003 and variant name "RM-937 VAR APAC TW CV BLACK", note the color doesn't really matter, the part that matters is RM-937 VAR APAC TW CV, the FW is the same, so the color won't make any difference,

2. Flash your Lumia 1520 using the software you usually use, in my case I use NPSTFS (Nokia Product Support Tool For Store in Nokia care Suite, you can also get all the FW versions from there), but you can use whatever you like, also it alert you that you are about to flash a FW version with a different Product code/region code, just say yes, as long as your Lumia 1520 is RM-937, they all have the same hardware, so they can all run the different variant and product code FWs that are available.

3. Now, this step is optional, but recommended if you're going to be using the phone as your regular phone, after flashing your phone, and on the 1st run, don't login and restore your back up, just skip all that, go to the about section and RESET YOUR PHONE, or alternatively, shut off your phone, press power+volume down button until an ! mark appears on screen, then press volume up, volume down, power button, volume down, the ! will disappear, the phone will vibrate, and restart showing the familiar cogwheels we all know so well, this means your phone will be hard Resetting, it's the equivalent to going to about page in settings and resetting your phone, this is recommended after every flash, because flash, only installs the FW/OS files, and then it boots straight up, while the reset, will check and organize the OS files and also format the memory, which will make the phone run smother, anyway, it's optional, you can skip it if you like, but it only takes 4-5 minutes, so, might as well.

4. Ok, now let's get down to business!! Now you may login and set your stuff as you would, this means restore your backups and all the stuff (I did it), or skip the restore, and just go straight to logging in with your MS accounts and getting the apps we need for the hack, my recommendation is: if you're planning on resetting the phone after installing Win10 TP, then do not restore, if you're not going to reset the phone after installing Win10 TP, then, restore (that's how I did it, since I reset the phone on STEP 3 after flashing the DENIM FW, there was no need to reset it again after installing the update).

5. Unlock your phone using the Devs SDK on the PC, and install/deploy Custom_WPSystem.xap (you can download this on the very 1st page of this thread).

6. Copy Custom_PfD.xap to your sdcard. And now we're done with the PC, everything else we will do from the phone.

7. Install windows insider (if you havent't yet) on the phone's memory, if by mistake you installed it on the sdcard, there's no problem, just go to storage sense-->apps, check Windows insider and move it to the phone memory.

8. Install PfD (preview for developers) on the sdcard, THIS IS KEY, it has to be on the sdcard, otherwise we can't swap the original PfD with the custom one, and we won't be able to change the registry values.

9. Start Custom_WPSystem on your phone, press the red colored bar that says "SD Card Permissions", this will open an explorer window, choose sdcard root, then press OK, the bar should turn GREEN indicating you now have access permissions on the sd card. Now without leaving Custom_WPSystem, go down to "select target app" (it's usually already PfD) and make sure that "Previe For Developers" is selected, now go down to the very bottom and tap "Select the XAP" under "Modding selected app", browse to the Custom_PfD.xap file on your sdcard that you copied on STEP 6, and select it, than tap "apply xap". It will take you to the applying page, and described what is happening, after this step is done Successfully, it will tell you something like, it's done, now try running PfD. If you get any errors/problems during this step it's probably because you didn't install PfD on the sdcard, but on the phone memory instead. So, make sure your PfD is installed on the sdcard.

10. Now, finally we will change the registry values so that the WINDOWS INSIDER app will "think" that our phone is electable for Win10 TP. So Start the new custom/modded PfD app that was hacked in the previous step, it should say new(as newly installed) and have a nice new marine green icon, start it, go to HKLM-->SYSTEM-->Platform-->DeviceTargetingInfo (it will turn green and say "You can write here) and change the following values/strings on the registry:

10.1 PhoneFirmwareRevision--> 02055.00000.14511.02202 and press "Write"

10.2 PhoneManufacturerModelName--> RM-984_1006 and press "Write"

10.3 PhoneMobileOperatorName--> 000-IN and press "Write" (THESE ARE THE 3 REGISTRY KEYS THAT THE TUTORIAL TELL YOU TO CHANGE, BUT IT DIDN'T WORF FOR ME SO I CHANGED 2 MORE, AND AFTER THAT IT WORKED, SO I'M ADDING THEM HERE)

10.4 PhoneHardwareVariant--> RM-984 and press "Write"

10.5 PhoneModelName--> Lumia 830 and press "Write"

We're done now!!

11. Just to make sure editing the registry worked, you can go to your about section on Settings and see if it says Lumia 830 on the phone model and RM-984. So, now FINALLY, go to WINDOWS INSIDER app, don't press Get builds, go to the ... on the bottom right corner, pull it up or press it, and choose--> sign in with different account-->Microsoft and enter the account you signed up for WINDOWS INSIDER with and login. it will check for builds automatically, and VOILA you'll get SLOW UPDATES and FAST UPDATES Option, choose the one you wish to enroll, confirm it, and the the app will restart your phone, after that, you'll be enrolled, you can go to Phone Update on settings and you'll be notified of a new update available, if you click details you'll see the glorious Windows 10 Technical Preview. ENJOY!!!

A few personal tips:

I've tried both the Slow and Fast Options, at first the Fast Option seemed to buggy, but after trying the slow one I've done the whole process again and went back to the fast updates one, seing that it seems to have more functional options, including the one to install any speech language while the slow version only allowed me to install Chinese from Taiwan.

Also I recommend that you don't skip step 3, and hard reset your phone after installing DENIM, and don't reset your phone after installing the Win10 TP update, cause it will reset your registry back to the default for your phone model, meaning that if your model is not supported by Win10 TP, you will stop being enrolled, and as of now, although you can install Custom_WPSystem.xap you can't get to the sd card root and Custom_PfD.xap from it due to file explorer limitations, so you can't edit the registry, also You'll have a really tough time installing apps from the store, and it will mess up your backups once it backs up your current configuration to the cloud. So bottom line, Hard reset your phone on STEP 3, restore your backups still on DENIM and then follow the rest of the steps, when you get Win10 TP, just update, and then keep on using it just like if you had gotten a regular update, DO NOT HARD RESET, that way all your apps from restore will be there, and you'll also keep the custom PfD (meaning you can still edit the registry), and you'll still be enrolled on the Win10 TP.

Remember, this always worked for me on a RM-937 Lumia 1520 with the specified product code and FW version, but if you're trying it on other Lumia models, the registry valus you alter are still the same, you just need to be lucky enough to find a product code for your model in which it will work, once again, I recommend a APAC version!!

I'm including a screenshot so you see the details of the Firmware version I specified!!! Not only it works on this one, as you get over 100MB free sys space with this versus the GB Country Variant I tried (and failed to get builds even following all steps), on GB variant you get ~630MB free sys space while on the APAC TW you get >730MB, so it's superior in many ways.

So, cheers and good luck!!!

Let me know if you have any doubts, and I'll try to help.