Inquiry on the authenticity of the Quran

God Bless you Joseph98,
I will try to answer the two questions from you.
The answer for number 1:
Allah has informed and explained in the Qur'an that whoever worships only to Allah, he will enter heaven, but whoever does not worship Him will go to hell.
We as intelligent beings will be able to draw the conclusion that someone will enter heaven or hell depending on how he/she follows His commands or not. Thus, God cannot be blamed because He has told us beforehand.
And all human beings who follow the teachings of Tauheed (absolute monotheism) of the Prophets before the Prophet Muhammad, they will get a guarantee to enter the heaven too.

The answer for number 2:
The Quran is a Holy Book that explains about previous Prophets and Books that they were people who only worship to Allah (one God).
And the relation to the New Testament is that the Quran will be difficult to be faked its contents, both added and subtracted.
Apart from that, the Quran contains verses that can provide information and that have been adapted to the development of human reason and civilization, such as verses related to science and technology, whereas in the previous Books there were none because human civilization had not as it is now.

This shows that Allah is All-Compassionate and Merciful to mankind. He will not send down His word except it has adjusted to the needs and circumstances of His creatures.

I apologize if this description is unclear, please ask again.
Thank you.

Asep