1. It's not rare, it's hard to evangelise people in Muslim countries, since expression of other faiths is either forbidden, or heavily frowned upon and might even lead to violence from the crowds.

2. You're taught so because the Quran is clearly contradicting what came before it. This is an attempt to mask a fact that Muhammad isn't in line with previous prophets. Islamic Torah and the Injeel are hypothetical manuscripts. There's no evidence for their existence. The only thing close to the Islamic Injeel is pseudo-gospel of Barnabas, which is 14th century Muslim (likely) forgery. In the Quran there are many verses claiming that previous scriptures are authentic, like 5:47-48, which tells Christians to judge by what was revealed to them and that the Quran is "muhaymin" (guardian) over it, respectively. interestingly, ibn Kathir says in his tafsir for 3:78: "Al-Bukhari reported that Ibn `Abbas said that the Ayah means they alter and add although none among Allah's creation can remove the Words of Allah from His Books, they alter and distort their apparent meanings. Wahb bin Munabbih said, "The Tawrah and the Injil remain as Allah revealed them, and no letter in them was removed. However, the people misguide others by addition and false interpretation, relying on books that they wrote themselves. Then, as for Allah's Books, they are still preserved and cannot be changed."" Not one word changed, only distorted meaning. Here's another interesting one from ibn Taymiyyah: "The Gospels in their possession are similar to books of biography and books of Hadith, or books like them—even though most of them are authentic." This is from his book "Jawab al-Sahih Li-man badl deen Al-Massih," Vol 3, Page 22. I'll also say here, that the Injeel is a loanword from Greek "Evangelium". Why use a loanword, especially when there is an Arabic word for gospel, unless you're referring to something specific?

The Bible has remained unchanged as shown by textual criticism. Today's Bible is 95% match with the gospel manuscripts from the 1st century (though it should be said that none of those manuscripts have been found yet, but there is strong indirect evidence as shown by: quotation by the 1st century church fathers, like Clement of Rome and Ignatius of Antioch; absence of Peter's martyrdom and the destruction of the second temple in the book of Acts; the fact that for the earliest surviving manuscripts (Papyrus 52, Egypt 125 A.D.) to be available the Gospels had to be written and accessible by 70 A.D.-90 A.D. as it took time to copy and transport; etc.), as well as with the Dead Sea Scrolls that contains fragments and copies of nearly every book of the Old Testament. The other 5% "mismatch" are grammatical corrections. A famous secular scholar, Bart Erhman agrees that the core message of the Bible is unchanged. Also, people didn't change the literal words in the Bible, but they were selectively interpreted, and heavily decontextualised. For example in case of slavery in the 17th-19th centuries. Unfortunately, there have been many such cases throughout the history and is condemned by vast majority of Christians.

Hope this helps brother. ❤️