Re: Who are the 24 elders
This is Mathhew Henry's commentary on the passage:
Four-and-twenty seats around the throne, were filled with four-and-twenty elders, representing, probably, the whole church of God. Their sitting denotes honour, rest, and satisfaction; their sitting about the throne signifies nearness to God, the sight and enjoyment they have of him. They were clothed in white raiment; the imputed righteousness of the saints and their holiness: they had on their heads crowns of gold, signifying the glory they have with him.