Try plugging your external speakers into the 3.5mm headphone jack on the device. Here is a link to other fixes for audio problems within Windows 10: https://www.makeuseof.com/tag/no-sound-7-tips-fix-audio-issues-windows-10/. If the issue continues, we recommend you call Lenovo Tech Support at: 877-453-6686.

Hi there, this device runs Android™ O, which is version 8. As for battery back-up, the tablet conveniently transitions to a charging dock, which will ensure it's always fully charged for use. If you ever have questions about your device, please do not hesitate to contact our customer service team @ 877-453-6686.

With regard to WiFi connectivity, the Yoga 730-15 4K model ships with the latest 5G 802.11AC WiFi. It is not just resetting your WiFi before pairing your Yoga 730-15 to the router, be sure your router has the latest firmware updates available at the router manufacturer's web site, especially if you are using an older b/g/n router. Second, be sure you have the latest version of Windows 10 on the computer and all the supporting BIOS files and drivers are up to date. You can easily accomplish this by scanning the computer with the Lenovo Utility software on the computer. 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 maximum RAM this configuration can support is 8GB DDR4-2666MHz RAM. There are two memory slots. The device ships with one 4GB stick in one memory slot.