What is the ruling on some people say that, Qur'an was revealed only for our Prophet (Sallallahu Alaihi wa Sallam) and Hijab also only for his wives and not for the other women?

Praise be to Allah, the Lord of the World; and may His blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.

Those who declare that the Holy Qur'an was sent down only for the Prophet (Sallallahu Alaihi wa Sallam), are required to repent to Allah, The Exalted. If they are ignorant, we have to teach them. If they are knowledgeable, their declaration constitutes Kufr (disbelief) and denial of what is stated in the Noble Qur'an and the sound Prophetic Sunnah and the accomplished fact among Muslims.
Allah Says (interpretation of meaning): {And We have not sent you (O Muhammad SAW) except as a giver of glad tidings and a warner to all mankind, …} [34: 28]. And He Says: {And We have sent you (O Muhammad SAW) not but as a mercy for the 'Alamîn (mankind, jinns and all that exists).} [21: 107]. He also Says: {… this Qur'ân has been revealed to me that I may therewith warn you and whomsoever it may reach. …} [6: 19].
Then, whoever says that the Qur'an rulings are special for the Prophet (Sallallahu Alaihi wa Sallam) or his message is special for some race, Arabs or non-Arabs, or for some time or place only, he accuses Allah and His Messenger of lying and becomes Kafir (disbeliever) and an outlaw of the Muslim fold.
As for one who declares that Hijab (covering the whole body of woman) is special for the Prophet's (Sallallahu Alaihi wa Sallam) wives, he has to produce an evidence, since it is proved among Muslim scholars that all Sharia rulings embrace all Muslims unless there is some exception with special proof.
For sure, there is no evidence that assigns such a matter in the Qur'an. Then, there is a comprehensive order that includes all Muslim women.
Allah Says (interpretation of meaning): {O Prophet! Tell your wives and your daughters and the women of the believers to draw their cloaks (veils) all over their bodies (i.e. screen themselves completely except the eyes or one eye to see the way). That will be better, …} [33: 59].
Thus, it becomes clear that the allegation that Hijab is special for the Prophet's (Sallallahu Alaihi wa Sallam) wives is false and a big lie.
We pray to Allah to guide us all to the right path.
Allah knows best.