Is John one of the 24 elders?

In Revelation 4 and 5 John sees the 24 elders. If the 12 Apostles are part of the 24 elders, does that mean that he saw himself in the future? What about the moment in 5:11-14 where all of creation worships Jesus. When does this event take place in relation to the Revelation timeline, as it doesn't seem to make sense to be before Tribulation?

The text never says John was actually present in the future. More likely, John was presented with visions of the future, and if so, we can safely assume the Lord didn't show John a vision of his future self. Regardless, John's memory of the scene would have been guided but the Holy Spirit so that he noted what was most important and necessary for his responsibility to record Scripture.

Regarding your second question...once again, John is experiencing a vision, so the timeline isn't concrete. That moment could be from any point in time, and most likely it is a vision of the same moment Paul describes:

Phil. 2:9 For this reason also, God highly exalted Him, and bestowed on Him the name which is above every name,
Phil. 2:10 so that at the name of Jesus EVERY KNEE WILL BOW, of those who are in heaven and on earth and under the earth,
Phil. 2:11 and that every tongue will confess that Jesus Christ is Lord, to the glory of God the Father.

This moment happens at the end of the Kingdom when the final judgment takes place for all humanity (Revelation 20), as Pastor Armstrong explains later in the Revelation course.