I have been trying to find out if the QBO developement version permit us to test features with Class, I don't see the option to turn on classes?

Hello there, @support7.

Thanks for visiting the Community. It’s my pleasure to help you enable the Class tracking feature in QuickBooks Online. 

The feature is only available in QuickBooks Online Plus. You can turn it on by following the steps below:
1.    Go to the Gear icon and select Account and Settings.
2.    Choose the Advanced tab.
3.    Click the Categories section.
4.    Select Track classes and click Save.
5.    Hit Done.

Here's an article for more information: How to set up and use class and location tracking.

If you can’t see this option in your account, it’s possible you’re using the QBO Simple Start or Essentials version. You might want to upgrade in order to use the feature. Click this link to know more about our updated pricing and features: Purchase QBO.

You can also to log in to your QuickBooks account and subscribe by going to the Account and Settings. Here’s how:
1.    Go to the Gear icon and select Account and Settings.
2.    Select the Billing and Subscription tab and go to the QuickBooks section.
3.    Click the Upgrade link next to your subscription plan.
4.    Enter your payment information and save the changes. 

Please see how do I upgrade my QuickBooks Online subscription for your reference. 

That should get you pointed in the right direction. Let me know if you have any questions, I'm more than happy to answer them for you. Take care and have a great day!
 

Hello support7,

  There is also the Intuit Developers Community where you can interact with other developers, just in case.