If God - who can see the future as "now" - does not have free will, how is it possible for humans to have?
Humans have free will because God gave fr will to humans. As I said before, God has a will, it is different from a human free will.
How our actions can be free if they are already set in time, and even God can not change them? Because if he could change them, he would not have seen them as they were in the first place.
It is not true that human actions are already set in time, and even God can not change them. Human actions are not set until a human makes a choice and causes those actions to occur. God could influence a human choice and change what we otherwise would have chosen if He wanted to, and maybe sometimes God does that.
God knows and sees everything, whether or not it was a choice we made or a choice that He influenced.
Again, it is impossible for God's messages to change over time if he knows the future,
Why couldn't God's messages humanity change over time if Hod knows the future? Since God knows the future, God has always known that the messages would change in the future. Indeed, many Bible prophecies are about what will happen in the future, what God has always known would happen, and that includes the messages that God would reveal through a new Messenger, who would be the return of Christ and the Messiah the Jews have long awaited.
let alone that he can not change (Malachi 3:6; James 1:17, etc.).
Malachi 3:6 For I am the Lord, I change not; therefore ye sons of Jacob are not consumed.
James 1:17 Every good gift and every perfect gift is from above, and cometh down from the Father of lights, with whom is no variableness, neither shadow of turning.
Those verses above mean that the attributes of God, God's character, does not ever change, but that does not mean God cannot change His messages to humanity.
If a doctor prescribes a different medicine for you than was prescribed 10 years ago, does that mean the character of that doctor has changed? No, it means that the needs of the patient have changed.
“The Prophets of God should be regarded as physicians whose task is to foster the well-being of the world and its peoples, that, through the spirit of oneness, they may heal the sickness of a divided humanity. To none is given the right to question their words or disparage their conduct, for they are the only ones who can claim to have understood the patient and to have correctly diagnosed its ailments. No man, however acute his perception, can ever hope to reach the heights which the wisdom and understanding of the Divine Physician have attained. Little wonder, then, if the treatment prescribed by the physician in this day should not be found to be identical with that which he prescribed before. How could it be otherwise when the ills affecting the sufferer necessitate at every stage of his sickness a special remedy? In like manner, every time the Prophets of God have illumined the world with the resplendent radiance of the Day Star of Divine knowledge, they have invariably summoned its peoples to embrace the light of God through such means as best befitted the exigencies of the age in which they appeared.”
Gleanings From the Writings of Bahá’u’lláh, p. 80
As an example, no God could ever give instructions like "fracture for fracture, eye for eye, tooth for tooth" and then years later say "if anyone slaps you on the right cheek, turn to them the other cheek also" and "love your enemies". This is all so terribly false and contradictory, in my opinion.
Why would scriptures that were revealed to an ancient people in ancient times still be valid for people living in modern times?
According to my beliefs, God can do whatever God wants to do because God is all-powerful. God is also all-knowing and all-wise, so God knows what humanity needs at any time throughout history. That is why the teachings of Jesus differ from those of Moses, as do some of the laws that were revealed.
Humans evolve spiritually and the world that we live in changes over time so why wouldn't God's message to humans change over time?
I believe that the world will be much different 1000 years from now, so God will send another Messenger with a new message that will be suitable for that new age. Meanwhile, I believe we should be following the message that God has revealed for the age we are living in.
“The All-Knowing Physician hath His finger on the pulse of mankind. He perceiveth the disease, and prescribeth, in His unerring wisdom, the remedy. Every age hath its own problem, and every soul its particular aspiration. The remedy the world needeth in its present-day afflictions can never be the same as that which a subsequent age may require. Be anxiously concerned with the needs of the age ye live in, and center your deliberations on its exigencies and requirements.”
Gleanings, p. 213
