The Devil has access to the throne of God until Revelation 12 at which time he is cast down to the earth
Yes, the Devil has access to God’s throne. He is the accuser of the brethren and stands before God day and night and accuses the brethren (Christians). In Revelation 12:10 however, he is cast down to the earth and can no longer make accusations in front of God regarding the people of God.
Then I heard a loud voice saying in heaven, “Now salvation, and strength, and the kingdom of our God, and the power of His Christ have come, for the accuser of our brethren, who accused them before our God day and night, has been cast down.” —Revelation 12:10
The example above was from the New Testament. The Old Testament is also quite clear as to whether the Devil has access to God’s throne. Job 1:16 states that Satan stands in the presence of God and presented himself before God when the sons of God came before Him. In this passage the sons of God were angels.
Now there was a day when the sons of God came to present themselves before the Lord, and Satan also came among them. —Job 1:6