The main reason to use a virtual machine as a sandbox is to test new software in a safe environment without risking the integrity of the host operating system. Using a virtual machine enables the testing of software and allows for the isolation of the software from the host system. Reference: CompTIA A+ Certification Study Guide, Tenth Edition, pg. 409

If the filesystem check shows that all files are accessible and the filesystem is clean, but a hard drive error message persists, it's possible that the hard drive is experiencing S.M.A.R.T. (Self-Monitoring, Analysis, and Reporting Technology) failure. This is a warning system built into hard drives to alert users of potential issues before they become critical. Reference: CompTIA A+ Certification Exam Core 1 Exam Objectives - 3.3 Given a scenario, troubleshoot mobile device issues

It is common for companies to place a data cap on the devices they provide to their employees, to control costs. If a user has exceeded the data cap, the phone may no longer allow internet browsing over a cellular connection. This is usually because the cellular data usage has exceeded the allotted amount for the particular plan the device is on, and the service provider has temporarily suspended the data connection.
It is unlikely that the child accidentally connected to a neighbor's WLAN because this would not affect the cellular data connection. Similarly, it is unlikely that the company's group policy has disabled the device, as this would likely affect all devices under the same policy. If the device's plan has been unpaid, the service provider would likely temporarily suspend all services, not just the cellular data connection.

NFC (Near Field Communication) is a technology used for short-range wireless communication between devices, typically used for contactless payments and authentication. In this scenario, the 13.56MHz frequency short band was implemented, and users can authenticate using their mobile devices, which requires NFC to be enabled on the device. Reference: CompTIA A+ Certification Exam Objectives 220-1001 - Mobile device network and device synchronization - 4.4