Here is a tutorial and complete guide on how to download and install the newly released iOS 9 Golden Master (GM) on iPhone 6 Plus, iPhone 6, iPhone 5s, iPhone 5c, iPhone 5, iPhone 4s, iPad 2 and iPod Touch for members of Apple Developer Program.

The iOS 9 GM comes just a week ahead of the public roll-out of the new software, which is set for 16 September. The GM release is the final version and contains same codes and features as the final build. The iOS 9 GM, carrying the build number 13A340, is pre-loaded on iPhone 6S and 6S Plus and reports suggest iPad Pro will ship with iOS 9.1 in November.

Below are the steps on how to download and install iOS 9 GM on iPhone, iPad and iPod Touch:

Step 1: Create a complete backup of your device using iCloud or iTunes before installing iOS 9 GM.

Step 2: To download the iOS 9 GM, you need to sign up for Apple Developer Program (a fee of $99 will be charged when you sign up). This also gives you access to early beta software releases from Apple.

If you already have an account, just sign in and proceed with step 3.

Step 3: Register your UDID with Apple for the iOS device you want to install the new GM seed on. If you don't know your UDID, all you need to do is plug in your device to iTunes, select your device and click on the serial number to view your UDID.

— Click on Certificates, Identifiers & Profiles in the main Member Center page.

— Under iOS Apps click on Devices, then click on "+" sign to register your UDID.

Step 4: Go back to the main Member Center page. Navigate to SDK > iOS > iOS 9. Then click on download. After this, select your device from the drop-down menu and begin downloading the required firmware file.

Step 5: After the download is complete, extract the downloaded zip file to get the .ipsw file for installation.

Step 6: Launch iTunes. Make sure you have the latest version of iTunes, if you don't have already.

Step 7: Install the GM seed on your device now. For Mac users, you can hold the Alt key and for Windows users, it is the Shift key. Click on the Restore iPhone button. iTunes will prompt you to select the .ipsw firmware file. Select iOS 9 file you downloaded earlier.

Step 8: The installation may take some time. Once it is done, your device will automatically reboot.

After a restart, your iDevice will be running the latest iOS 9 GM. You can start testing the new apps and features in the latest OS build.

iOS 9 GM (direct download links)

Features of iOS 9 GM

Siri Advancements: The new update is said to have boosted Siri capabilities and features. The feature will be 40% faster and accurate.

Proactive Assistance: Your iPhone will now be able to suggest a ton of actions based on your location like connecting your device to a headphone or your care, suggest turning on your music player or audiobook accordingly. You can also make flight reservations based on your calendar events. When you get a call from an unknown number, the iOS will suggest who may be calling, based on whether or not the number has ever been mentioned in any mail stored on your device. Also, all contact details received will automatically be stored on your Contacts list.

Wallet App: Improved features in the Passbook, a hub for credit and debit cards, reward cards, boarding passes and more.

News App: It has also got a brand new News app which displays the latest happenings. That is not all, it displays news based on your interests.