'The first resurrection,' mentioned in Revelation 20:5, 6, does not mean a first resurrection, but the essence and primary part of resurrection, which is salvation and eternal life. There is only one resurrection to life. A second does not happen, and is not mentioned anywhere in the Bible.

(References: Apocalypse Explained 6; Apocalypse Revealed 851; Revelation 20:5-6)

The Lord's love is the sun of heaven, and it is natural for us to look above ourselves to the sun of this world in thinking about the Lord. It follows, then, that to be closer to the Lord we would climb into the highest places -- and indeed, people have been worshiping on mountains for ages. In fact, even steeples on modern churches are symbolic mountains. It makes sense, then, that a mountain in the Bible represents love to the Lord, the highest, purest love we human beings can experience. Mountains can also represent the desire for good that comes from the love of the Lord. Hills, meanwhile, represent a love of other people and a caring for them, and when "mountains" is used in the plural it generally represents both loves.