List of devices that are eligible for the update : » Click to show Spoiler - click again to hide... «
Lumia :
* 1520
* 930
* 640
* 640 XL
* 730
* 735
* 830
* 532
* 535
* 540,
* 635 1GB
* 636 1GB
* 638 1GB
* 430
* 435
What about other devices that are not on this list?» Click to show Spoiler - click again to hide... «
As Windows 10 delivers significant new innovations, many older devices are not able to successfully upgrade without an impact on the customer experience. Our goal is to only offer the Windows 10 upgrade to devices that we are confident can continue to deliver a good customer experience.
If you already have the Windows 10 Mobile Insider Preview build on your device, you may keep using your device in an unsupported state. We will not be offering build updates beyond the Current Branch build 10586. At some point in the future these devices will also stop receiving updates to the Windows 10 Mobile Insider Preview build. In order to recover the devices back to a supported build of Windows Phone 8.1, you may use the Windows Device Recovery Tool.
TLDR version : You're not going to get the official update. The only way for you to get W10M is through Insider Program, but even then you'll be stuck at build 10586 and further build will no longer be available to your devices.
How to download the update (it's not on Settings > Phone Update) : » Click to show Spoiler - click again to hide... «
* Download the
Upgrade Advisor app (QR code below)
* The size of the update is 1.4GB (Wi-Fi is required)

Feature deprecationWhen you install the Windows 10 upgrade, some features currently on your device will be modified or removed, including the following:
* Notifications for missed calls, messages, and emails on contact tiles is not supported.
* Me Tile and Me Card are no longer supported.
* Cortana can no longer search for apps, setting, email, text messaging, contacts
* QR Codes on the device and can no longer open apps through voice commands.
* "Hey Cortana" is no longer available on some upgraded devices.
* Group tiles can no longer be used to receive social networking status updates
* Indoor Maps are no longer available for some locations
* Certain enterprise features, including Data Protection Under Lock, are not available
* Outlook Mail app cannot open .EML attachments.
* Outlook Calendar app does not support Tasks.
* MDM capability to prevent saving and sharing Office documents not supported.
References :» Click to show Spoiler - click again to hide... «
This post has been edited by Assassin's: Mar 18 2016, 02:07 AM