Are there any apps for Android or iPad that have full VST support? From what I can tell, every VST must be specially compiled for use on these systems, so the answer would be no. But is that correct?
The VST SDK doesn't exist for Android or IOS, so there can't be apps with true VST support. Chris Randall explains on his excellent blog (warning,
may contains profanity!).
What ObscureRobot said in 2013 is now outdated information. The VST 3 SDK now exists for iOS 8/9. It's GPL3 so I can't see why someone couldn't port it to Android. https://github.com/steinbergmedia/vst3sdk
As for your question, is there any "ios app with full vst support"? Steinberg has a list of apps that use VST3. https://www.steinberg.net/en/products/mobile_apps.html Although some of the apps obviously used the SDK for hosting VST, as far as I can tell, there are not (yet) any iOS apps with full third-party VST support.
Indeed, the Auria iOS app (https://itunes.apple.com/au/app/auria-mobile-music-production/id524122834?mt=8) that is the topic of that blog posted by ObscureRobot does not list VST support in its product page. On the other hand, it does offer, "Third party plugin support available via in-app purchase," which may well utilise the VST technology. As I understand your question, it's "full VST support" but the only supported VSTs are apparently the in-app purchases.
It's fairly easy for a developer to port a plugin to Auria, as we use VST 'under the hood'. http://auriaapp.com/forum/viewtopic.php?f=19&t=12311&start=0