Google Nexus 7 (2013) just received upgrade support from OctOS custom ROM for Android 6.0.1 Marshmallow. The custom build offers a couple of exclusive features on top of a few originals.
OctOS custom ROM offers exclusive features and latest tweaks based on Android 6.0.1 Marshmallow for Google Nexus 7 (2013). However, OctOS is still in beta version so bugs will more likely occur once in a while. Developers assure Nexus 7 (2013) device owners that this will be stable, fast and smooth when the final version is released in the coming weeks.
Before installing OctOS on Google Nexus 7 (2013), take note of the following reminders and prerequisites first:
1. Do not use any other variant not prescribed. Otherwise, it may cause damage.
2. Install TWRP Recovery here.
3. Back up all necessary data here.
4. Download USB driver here.
5. Installing the any custom ROM induces risk of damaging device. Neither this site nor developers of the OctOS ROM will be held responsible for such damage.
To download and install Android 6.0.1 OctOS Marshmallow to Google Nexus 7 (2013):
1. Download on PC the Android 6.0.1 OctOS ROM here and Google Apps here.
2. Connect phone to PC using the USB cable.
3. Copy then paste downloaded ROM to phone's memory or SD card.
4. Switch off phone and plug it out from the PC.
5. Go to Recovery Mode by press holding volume up, home and power buttons.
6. Choose 'Wipe' to delete of data and 'Swipe to Factory Reset'.
7. Go to Advance and choose 'Wipe cache/dalvik' button.
8. Go to main menu and choose 'Install'. Choose the copied ZIP file on the phone.
9. Choose 'Swipe to Confirm Flash'.
10. Wait for the installation to complete then go to +++++Go Back+++++.
11. Choose 'Reboot System'.
Check the new software version on Settings > About phone.