1. Since Jesus is Lord God, Did Lord God give specifically unto himself the throne of his earthly father David? Can him be replaced with himself in Luk 1:32?
Luk 1:32 He shall be great, and shall be called the Son of the Highest: and the Lord God shall give unto him the throne of his father David:
I believe that is correct.
I believe You are incorrect. God never had the throne until He gave it to Jesus.
God never had Kingdom of God until he gave it to Jesus?
2. If someone says that someone else is greater than them, does that mean that someone is lesser than that someone else?
I believe you are incorrect. There are not two someones. God is one. The fact is that God outside of Jesus is greater by dint of the fact that He is everywhere and that God in Jesus is just in one place.
Joh 13:3 Jesus knowing that
the Father had given all things into his hands, and that he was come from God, and went to God;
Joh 14:28 Ye have heard how I said unto you, I go away, and come again unto you. If ye loved me, ye would rejoice, because
I said, I go unto the Father: for my Father is greater than I.
Joh 16:26 At that day ye shall ask in my name: and I say not unto you, that I will pray the Father for you:
Joh 16:27 For the
Father himself loveth you, because ye have loved me, and have believed that I came out from God.
Joh 16:28 I came forth from the Father, and am come into the world:
again, I leave the world, and go to the Father.
Joh 16:29 His disciples said unto him, Lo,
now speakest thou plainly, and speakest no proverb.
Joh 16:30 Now are we sure that thou knowest all things, and needest not that any man should ask thee:
by this we believe that thou camest forth from God.
Joh 16:31 Jesus answered them, Do ye now believe?
4. There are many lords in the bible with our God being the greatest of all who is Possessor / Lord of Heaven and Earth.
I believe the Lordship is equal. Try to remember Jesus did not say the Father was greater in all ways. He would not have to for the statement to be true.
1Co 8:5 For though there be that are called gods, whether in heaven or in earth, (as there be gods many, and lords many,)
Joh 10:29 My Father, which gave them me, is greater than all; and no man is able to pluck them out of my Father's hand.
Joh 8:40 But now ye seek to kill me, a man that hath told you the truth, which I have heard of God: this did not Abraham.
1Co 11:3 But I would have you know, that the head of every man is Christ; and the head of the woman is the man; and the head of Christ is God.
Mat 11:25 At that time Jesus answered and said, I thank thee, O Father, Lord of heaven and earth, because thou hast hid these things from the wise and prudent, and hast revealed them unto babes.
Rev 3:5 He that overcometh, the same shall be clothed in white raiment; and I will not blot out his name out of the book of life, but I will confess his name before my Father, and before his angels.
Rev 3:12 Him that overcometh will I make a pillar in the temple of my God, and he shall go no more out: and I will write upon him the name of my God, and the name of the city of my God, which is new Jerusalem, which cometh down out of heaven from my God: and I will write upon him my new name.
Rev 3:21 To him that overcometh will I grant to sit with me in my throne, even as I also overcame, and am set down with my Father in his throne.