This phrase clarifies who on the earth will worship the beast. It can be stated in active form. Alternate translation: "those whose names the Lamb did not write ... in The Book of Life" or "those whose names were not ... in the Book of Life" (See: [[rc://en/ta/man/translate/figs-activepassive]])
The author speaks of the world as if it were a building set on a foundation. Alternate translation: "when God created the world" (See: [[rc://en/ta/man/translate/figs-metaphor]])
A "lamb" is a young sheep. Here is it used symbolically to refer to Christ. See how you translated this in [Revelation 5:6](../05/06.md). (See: [[rc://en/ta/man/translate/writing-symlanguage]])