I have downloaded Windows 10 technical preview. It was around 2 Gb. If Microsoft releases new version/build of windows 10, will I have to download whole 2 Gb file or the update file size is smaller?
It's hard to say for sure what Microsoft have planned, but I'd imagine that you'll have to download the whole update when the final release comes - especially if you don't wish to remain in the Windows Insider program. The size of the update will likely vary given that we're still just in the preview stage.