If you long press on a speed dial you can drag it to the trash can. That way you can <font color=gray>recover</font> any speed dial you want.

Seem the same ting as on iPhone, thanks for point out.

USB, you should already know. The failure he mentions is very real, these USB thumb-drives can and do fail and when they do, the failure is usually catastrophic loss of data stored on the device. Almost no way to <font color=gray>recover</font> them if you use these , use more than one-- they're cheap enough-- so you have at least one that is good.
About the rest: LAN is Local Area Network. Basically, any computer in your home network, any printers attached and so on.
NAS= Network-Attached-Storage. That external hard-drive comes to mind.
RAID= Redundant Array of Independent Disks. OK, use more external hard-drives for your backup. One of them should work.
I'm a big fan of not making the thing more complicated than it has to be. I make copies of my files on the USB drive, so in the event that I need to access them it's not that hard. I can retrieve these files on any USB-equipped computer.

I totally agree ! There is no need to make things complicated. Indeed, a portable hard drive is enough for most users in most cases. Another convenient way is to use cloud service, like Google Drive, Dropbox, OneDrive, etc...