Can i use my Nexus 7 tablet, not a Nexus 7 II, with my mavik?  

Theoretically, yes you can. However, I don't recommend it. Performance of this tablet is kind of poor. I guess you would experience some lags..

Nexus 7 tablet not on the support list, but it doesn't mean that it can't run DJI GO/DJI GO 4 smoothly. You can try if you have this device in your hand and hope others who have the device will provide some tips on it.
Sometimes we would recommend using the mobile device on our test list because engineers had tested to run DJI GO/DJI GO 4 on that mobile devices and they performed fine. Hope it provides you with some hints.

About the only thing you can do is try it, many devices that are not listed as compatible still work fine. If google play say your device is not compatible then google dji go APK and download thru a mirror. Just make sure you click unknown sources in settings...