Was God's land promise to Abram unconditional?

God called Abram, and he went in Gen 12:

6a When they came to the land of Canaan, 6 Abram passed through the land to the place at Shechem, to the oak of Moreh. At that time the Canaanites were in the land. 7 Then the LORD appeared to Abram and said, “To your offspring I will give this land.” So he built there an altar to the LORD, who had appeared to him.

Click to expand...

God promised to give Abram's offspring some (physical) land. It was a gradual revelation. Another detail was added in the next chapter, Gen 13:

14 The LORD said to Abram, after Lot had separated from him, “Lift up your eyes and look from the place where you are, northward and southward and eastward and westward, 15 for all the land that you see I will give to you and to your offspring forever.

Click to expand...

H5704-forever was polysemantic. It did not always mean time going on to infinity

Genesis 15:

17 When the sun had gone down and it was dark, behold, a smoking fire pot and a flaming torch passed between these pieces. 18 On that day the LORD made a covenant with Abram, saying, “To your offspring I givec this land, from the river of Egypt to the great river, the river Euphrates

Click to expand...

The fire and smoke symbolized the theophany. God alone certified this covenant, and the promised land did not depend on Abram. This covenant was fulfilled by Joshua.

Genesis 17:

8 I will give to you and to your offspring after you the land of your sojournings, all the land of Canaan, for an everlasting [H5769] possession, and I will be their God.”

Click to expand...

H5769-olam-forever was also polysemantic.

Abraham instructed his servant in Genesis 24:

7 "The LORD, the God of heaven, who brought me from my father's house and my native land, who spoke to me and promised me on oath, saying, 'To your offspring I will give this land'--He will send His angel before you so that you can take a wife for my son from there."

Click to expand...

Abraham didn't mention the forever part.

Genesis 26:

2 The Lord appeared to Isaac and said, “Do not go down to Egypt; live in the land where I tell you to live. 3 Stay in this land for a while, and I will be with you and will bless you. For to you and your descendants I will give all these lands and will confirm the oath I swore to your father Abraham.

Click to expand...

Was God's land promise to Abram unconditional?

Yes, and it was fulfilled already. However, there could be further fulfillment.

Did God promise to give his descendants the land forever unconditionally?

Probably not.

Moses explained in Lev 18:

26 But you shall keep my statutes and my rules and do none of these abominations, either the native or the stranger who sojourns among you 27(for the people of the land, who were before you, did all of these abominations, so that the land became unclean), 28 lest the land vomit you out when you make it unclean, as it vomited out the nation that was before you.

Click to expand...

Jeremiah 7:

5 If you really change your ways and your actions and deal with each other justly, 6 if you do not oppress the foreigner, the fatherless or the widow and do not shed innocent blood in this place, and if you do not follow other gods to your own harm, 7 then I will let you live in this place, in the land I gave your ancestors for ever and ever.

Click to expand...

There was a condition in order to keep the land continuously.