Android and iOS App issues fixing and improvements

Android and iOS app that I have needs to be improvised. Some issues need to be fixed such as, 1) App not visible to some Android devices. iOS app is displaying and is fine 2) SECURE ENCRYPTED Downloading of the video for offline viewing needs to be perfected. Currently there are issues such as download fails or during download page needs to be kept open or download progress indicator is not accurate 3) Test questions to be automatically downloaded SECURELY & ENCRYPTED on device for offline practising. And offline data to be synchronised with website DB 4) Test functionality GUI to be improvised for ease of use 5) BigBlueButton training joining function to be added so user can join virtual training course from Android or iOS device or view recordings from their virtual devices 6) Course validity and expiry to be implemented so user can't access the product after certain date or certain attempts. Even when user disconnects internet after first download of content. Number of Attempts and validity is checked locally and access stopped after expiry. Attempt data to be uploaded to website DB the moment user connects to internet. 7) App should be able to be downloaded on any Android or iOS devices and be able to open it, login and use the app without any resolution etc.. issues 8) The App has setting of Wifi Only mode On or Off. When Off user can also download videos or play videos via SIM. THis functionality should work seamlessly. There should be a notification when user is trying to play via SIM with a possibility to disable notification going forward. 9) Currently downloaded videos or questions are very secure and encrypted. This should be maintained so that user doesn't download it from the smart device and even though user does it can't play it without the app. Please provide your fixed price quote.