A:AnswerYes it can. It runs macOS which is Apple’s full fledge desktop operating system. If Home Office or 365 is purchased, once you download Excel from the App Store and sign in, you can make spreadsheets.
A:AnswerYes, steam games which support BOTH MacOS and Apple Silicon will be supported on the Neo. Check reviews and performance estimates for the games you play first though.
A:AnswerUnless there is a 16gb+ version, no. The second you change anything about the internals of an Apple computer, you void the warranty. They often solder many of the components to the motherboard to prevent changes like this.