https://www.reddit.com/r/chevyspark/comments/6yljr8/_/dtjhj80
Go to the home screen on the head unit.
Tap the upper right corner on the screen repeatedly until a “Keypad” screen shows up, prompting for a password.
On 2017’s (and probably 2016’s as well) enter “20130822” and press “OK”
There’s no feedback here. Just tap the “back” arrow in the upper left.
The Settings Menu will now have “Development Helper” and “Development Mode” menus. Enjoy!
Leaving the key off long enough the head unit needs to reboot on subsequent startup reverts the unit
No idea if this applies to our unit, but seemed plausible.
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https://www.chevymalibuforum.com/threads/2017-7-mylink-developer-mode-access.96265/#/topics/96265

Ok so I can confirm that 20130822 works on a 2017 Malibu Ls with 7" Mylink...
Outlined below are the steps:

1. Turn on your radio, turning on the car is not necessary

2. Hit the home button (looks like a house)

3. Tap 10x in the upper right hand corner till it prompts you for a code

4. Enter 20130822 hit ok!

5. Nothing happens, so hit the back button

6. Tap on Settings and scroll all the way to the bottom! Whats that you see? Developer Helper and Development Mode?

Checked out everything there some very interesting stuff... mainly testing stuff, want to see if there is a way to access Windows CE environment

Please remember this is at your own risk and I am not responsible if you brick your radio due to your tinkering.