The Gospel of Eisa is not the same as the four Gospels.
It is pretty obvious that the Torah is not the Torah of Musa, since it includes the death of Musa. No idea when the changes were made though.
The Gospel of Nabi Isa (a.s) certainty is not the four Gospels but these four Gospels were in their full existence during the time of Nabi Mohammed (s.a.w.w) and Nabi Mohammed (s.a.w.w) considered them Holy Books as Christians were called People of the Book i.e. those who received GOD'S Holy Book.
I've never seen a narration saying that the canonical gospels (Matthew, Mark, Luke and John) of the Christians are holy books. This has never been said, to my knowledge that is. Secondly they were called Ahl al-Kitab because they were people who had received revelation but they had turned away from it in favour of their desires as Allah says
2:145
And if you brought to those who were given the Scripture every sign, they would not follow your qiblah. Nor will you be a follower of their qiblah. Nor would they be followers of one another's qiblah. So if you were to follow their desires after what has come to you of knowledge, indeed, you would then be among the wrongdoers.
5:13
So for their breaking of the covenant We cursed them and made their hearts hard. They distort words from their [proper] usages and have forgotten a portion of that of which they were reminded. And you will still observe deceit among them, except a few of them. But pardon them and overlook [their misdeeds]. Indeed, Allah loves the doers of good.
It is the fact that they hide what is in their books. Did you know for example that many ancient scrolls of the Gospels and Old testament have been bought and hidden by the Vatican? And this is in agreement with what Allah says in the Qur'an as he mentions that they hide and distort the scriptures.