IF, through conquest, Abraham had laid claim to the land during his lifetime then when he died his son Issac would inherit the land, and so on as long as it remained in the family. Acts 7:5 simply means Abraham didn't receive any inheritance in the land (not even a footstep) while he was living. So, how could he include any of the [Promised] land in a will to pass on to Issac and so forth (except the burial cave).
Where do you find in Genesis that Abraham had a will stating that Issac was to inherit the [Promised] land? The only site Abraham purchased (from the Hittites) was a burial plot (cave) for his wife Sarah.
Abraham had not laid claim to any of the [Promised] land through conquest during his lifetime. It was only much later that the twelve tribes (through conquest) were able to settle down having laid claim to a portion of
their Promised Land. The full extent of the Promised Land has yet to be fully realized.
There are two covenants. The first does not give to Abraham, but his seed. in particular the fourth generation of his seed
Ge 15:18 In the same day the LORD made a covenant with Abram, saying,
Unto thy seed have I given this land, from the river of Egypt unto the great river, the river Euphrates:
But The second covenant spake to Abraham as well.
Ge 17:8 And I will give
unto thee, and to thy seed after thee, the land wherein thou art a stranger, all the land of Canaan, for an everlasting possession; and I will be their God.
Actually however the second covenant was established first, in Isaac.
Paul teaches that nothing can be added to nor taken away concerning this covenant.
Ga 3:15 Brethren, I speak after the manner of men; Though it be but a man’s covenant, yet
if it be confirmed, no man disannulleth, or addeth thereto.
So I am thinking the promise of a royal kingpriest was established in Isaac to Abraham from that point on.
Ge 17:21 But my covenant will
I establish with Isaac, which Sarah shall bear unto thee at this set time in the next year.
Gen 22:16 And said, By myself have I sworn, saith the LORD, for because thou hast done this thing, and hast not withheld thy son, thine only son:
17 That in blessing I will bless thee, and in multiplying
I will multiply thy seed as the stars of the heaven, and as the sand which is upon the sea shore; and thy seed shall possess the gate of his enemies;
Ex 6:4 And
I have also established my covenant with them, to give them the land of Canaan,
the land of their pilgrimage, wherein they were strangers.