In case you had a Build 10512 on your phone you will need to update to Build 10514 first and then to the latest Build 10536.  The update has bunch of changes listed below and the major update to the Photos app (version 15.9).

Here are some of the improvements Microsoft made since the last build:

• Insider Hub is now included again.
• Mobile hotspot functionality has been fixed.
• Voice input has been updated to add support for Japanese and English (India) speech recognition.
• Single hop updates are again available from Windows Phone 8.1 to Windows 10 Mobile Insider Preview for all devices.
• Two-factor authentication is fixed when setting up a device for both text and phone authentication.
• Start screen will successfully load instead of failing with “Loading …” displayed in a loop until device was rebooted. (We are still tracking down an issue were it may show “Loading …” for a few seconds.)
• Quite Hours\Do Not Disturb has been fixed.
• Delay in showing date and time on Lock screen has been improved.
• Pinch and zoom in Maps now works as expected.

This update introduces a folder view that makes it easy for you to see your OneDrive and PC folders in the Photos app. On your phone, you can also see folders on your SD card. The update debuts on the phone first and it will make it soon to the desktop version too.

The new Build 10536 introduces a one hand mode for larger phones. Once you hold and press the Start button, the screen will slide down so you can reach items at the top of your screen.

This is an insider preview release so there are a bunch of unpolished bugs so be prepared. Since Microsoft plans to launch new line of Lumia's on October 10th, we expect that the final version of Windows 10 mobile should be ready by then.