2 Grace to you and peace from God our Father and the Lord Jesus Christ. (WEB)
Here, Paul sends them a letter that would give them if they follow it, God’s favor and inner peace by obeying God’s Word.
Paul uses the word “God” for the Father and “Lord” for Jesus Christ. Both God and Lord refers to the same person, Yahweh.
God means to be sovereign, supreme ruler of all and can do what He pleases.
Lord means master, to be supreme and ruler overall with full authority.
For Yahweh your God, he is God of gods, and Lord of lords, the great God, the mighty, and the awesome, who doesn’t respect persons, nor takes reward. (WEB)
These will war against the Lamb, and the Lamb will overcome them, for he is Lord of lords, and King of kings, and those who are with him are called chosen and faithful.” (WEB)
24 Now to him who is able to keep them from stumbling, and to present you faultless before the presence of his glory in great joy
“Now to him who is able to keep them from stumbling” God Himself keeps those who are His from abandoning Him through His mighty power. He does this by convicting us when we commit sin and stray from his presence.
“to present you faultless” The word faultless means to be without sin [being forgiven]. But, according to the context, it is in reference to being faithful to the end and not giving up on one’s faith in Jesus Christ.