It is possible this is due to a recent Windows 10 update that also requires a separate update of the BIOS files and drivers on the computer. You can easily check this by scanning the device with the Lenovo Utility software installed on the device. This system has Lenovo utilities installed to help maintain the health of the device and keep the operating system software up to date. Type "Lenovo Vantage" in the Cortana Search window (if Lenovo Vantage is not installed on your device, you can download the APP and install it now). Select Lenovo Vantage from the list. In the window that opens, click on "Health and Support". In the expanded menu, select "Hardware Scan" In the window that opens, select "Run Quick Tests". This will scan your entire system for errors. Follow any directions that may pop up. If the problem continues after this scan, now click on "System Update". First select Windows update from the menu. Scan your system to be sure you have the latest version of Windows 10. Once that scan is complete, select "Additional Updates". This will scan your device to be sure there are no new BIOS/Driver updates needed. Follow any instructions that may pop up. If the issue still continues after these updates, we recommend you call Lenovo Tech Support at: 877-453-6686 for additional help. For 2018, Lenovo retained its place for a second year as the best laptop vendor:
https://www.laptopmag.com/articles/laptop-brand-ratings

No, the Yoga Book C930 does not have LTE capability.

That will depend on the software you will be using and the requirements and compatibility of that software. We recommend you check with the software publisher's web site for the specific software you will be using on the computer, for their compatibility with Windows 10 S-Mode operating system (you can switch to Windows 10 Home 64-bit operating system, without any additional cost) and the minimum/recommended hardware requirements (Is a Graphics card required, the processor speed and the minimum required system RAM and the minimum available hard drive space) to run their program, then compare those requirements to this system's configuration.

Switching from S-Mode to the standard Windows 10 Home 64-bit operating system will not slow the device down. The software you install on the device after the switch may. We recommend you check with the software publisher's web sites for the software you want to install on the computer, for their compatibility with Windows 10 Home 64-bit operating system and the minimum/recommended hardware requirements (Is a Graphics card required, the processor speed and the minimum required system RAM and the minimum available hard drive space) to run their program, then compare those requirements to this system's configuration. Please keep in mind, this is an entry level, light use system with its Intel Celeron processor. It is not meant for multi-tasking or demanding programs. It is good for Microsoft Office (there is a 1-year free subscription included with this device) and light internet browsing.