Question 4
Does Revelation call us back to this sign or seal?
Bible
Revelation 14:7
"Fear God and give glory to Him; for the hour of His judgment is come; and worship Him that made heaven, and earth, and the sea."

Answer
In Revelation 14 we find 3 angels with three messages for earth. The first angel's message, which is in the text above, has a direct quote from the Sabbath commandment. The message is "Worship Him who made heaven and earth and the sea". Those are the exact same word we just read in Exodus 20, which is the commandment to keep the Sabbath day holy. If Revelation is a book of symbols, the key to unlock the meaning of this symbol is found in the Sabbath commandment. It represents a message calling us back to worshiping God by keeping the memorial of His creation. Keeping the 7th day Sabbath holy is what God gave us as the memorial of His creation.