Yes. The scripture says so:
Gen 3:15 And I will put enmity between thee and the woman, and between thy seed and her seed; it shall bruise thy head, and thou shalt bruise his heel.
Gen 3:21 Unto Adam also and to his wife did the LORD God make coats of skins, and clothed them.
Gen 4:4 And Abel, he also brought of the firstlings of his flock and of the fat thereof. And the LORD had respect unto Abel and to his offering:
Mat 23:35 That upon you may come all the righteous blood shed upon the earth, from the blood of righteous Abel unto the blood of Zacharias son of Barachias, whom ye slew between the temple and the altar.
Luk 11:51 From the blood of Abel unto the blood of Zacharias, which perished between the altar and the temple: verily I say unto you, It shall be required of this generation.
Heb 11:1 Now faith is the substance of things hoped for, the evidence of things not seen.
Heb 11:2 For by it the elders obtained a good report.
Heb 11:3 Through faith we understand that the worlds were framed by the word of God, so that things which are seen were not made of things which do appear.
Heb 11:4 By faith Abel offered unto God a more excellent sacrifice than Cain, by which he obtained witness that he was righteous, God testifying of his gifts: and by it he being dead yet speaketh.
Heb 12:24 And to Jesus the mediator of the new covenant, and to the blood of sprinkling, that speaketh better things than that of Abel.
Rev 13:8 And all that dwell upon the earth shall worship him, whose names are not written in the book of life of the Lamb slain from the foundation of the world.
2Co 4:4 In whom the god of this world hath blinded the minds of them which believe not, lest the light of the glorious gospel of Christ, who is the image of God, should shine unto them.
2Co 4:6 For God, who commanded the light to shine out of darkness, hath shined in our hearts, to give the light of the knowledge of the glory of God in the face of Jesus Christ.
Yes. See:
Gen 4:26 And to Seth, to him also there was born a son; and he called his name Enos: then began men to call upon the name of the LORD.
Joe 2:32 And it shall come to pass, that whosoever shall call on the name of the LORD shall be delivered: for in mount Zion and in Jerusalem shall be deliverance, as the LORD hath said, and in the remnant whom the LORD shall call.
Act 2:21 And it shall come to pass, that whosoever shall call on the name of the Lord shall be saved.
Rom 10:13 For whosoever shall call upon the name of the Lord shall be saved.
Abraham, Moses, Joshua, etc spake to the Son of God directly, and it is written of them:
Gal 3:8 And the scripture, foreseeing that God would justify the heathen through faith, preached before the gospel unto Abraham, saying, In thee shall all nations be blessed.
Joh 8:56 Your father Abraham rejoiced to see my day: and he saw it, and was glad.
Consider Abraham with Isaac on the mount, and the sacrifice, and the Ram.
Moses and the Israelites had the same Gospel:
Heb 4:2 For unto us was the gospel preached, as well as unto them: but the word preached did not profit them, not being mixed with faith in them that heard it.
Isaiah had it:
Isa 52:7 How beautiful upon the mountains are the feet of him that bringeth good tidings, that publisheth peace; that bringeth good tidings of good, that publisheth salvation; that saith unto Zion, Thy God reigneth!
along with many others from the beginning (Seth, Noah, Job).
Hebrews 11 itself on the whole, among other places already cited:
Heb 11:1 Now faith is the substance of things hoped for, the evidence of things not seen.
Heb 11:2 For by it the elders obtained a good report.
Heb 11:3 Through faith we understand that the worlds were framed by the word of God, so that things which are seen were not made of things which do appear.
Heb 11:4 By faith Abel offered unto God a more excellent sacrifice than Cain, by which he obtained witness that he was righteous, God testifying of his gifts: and by it he being dead yet speaketh.
What did Abel "hope for"? What could he not yet "see" directly? The event of the Cross, through the sacrifice of the "lamb" "slain from the foundation of the world", but he did see it by faith, even in the clothing of his parents, Adam and Eve (Genesis 3:21), and so offered of the "firstlings" of his flock, in the "seed" to come (Genesis 3:15)
Following God and keeping His commandments is always required, from Adam to the last man, see:
Ecc 12:13 Let us hear the conclusion of the whole matter: Fear God, and keep his commandments: for this is the whole duty of man (Adam).
Ecc 12:14 For God shall bring every work into judgment, with every secret thing, whether it be good, or whether it be evil.
The Gospel is not contrary to that, but in harmony with it.
They understood as far as they needed to then, and saw by faith.
Yes. They are partly correct, just got the timing incorrect. They desired political deliverance, politcal reforms, rather than true deliverance (from sin, Matthew 1:21; 1 John 3:4), and character/heart reform, even as it is now, for events are already repeating for the last time.