Sounds like a cult leader. All his followers must follow his god's rules, but the rules don't apply to him. In contrast, Jesus followed all the rules. And Biblical prophets who did not obey God from time to time were openly called out for not doing so. Such people included Abraham, Moses, David, etc.
And according to you, the "last testament", aka quran, is not meant for mahomet, since he's not required to obey his own revelations.
Again, there are thousands of manuscripts of the new testament, in numerous languages.
The New Testament has been preserved in more manuscripts than any other ancient work of literature, with over 5,800 complete or fragmented Greek manuscripts catalogued, 10,000 Latin manuscripts and 9,300 manuscripts in various other ancient languages including Syriac, Slavic, Gothic, Ethiopic, Coptic and Armenian. The dates of these manuscripts range from c. 125 (the 52 papyrus, oldest copy of John fragments) to the introduction of printing in Germany in the 15th century.[citation needed]
https://en.wikipedia.org/wiki/Biblical_manuscript
Anyone is free to go study them. Manuscripts that were rejected from the New Testament are also around. And people are free to read them. Your moslem prophet mahomet did. That's why you can find Gnostic teachings in his ramblings which later formed the quran.
In contrast, there is ZERO surviving manuscripts from the scribes who copied down mahomet's ramblings. All burnt and destroyed by caliph uthman.
There are also ZERO surviving copies of quran from abu bakr and uthman's era. The oldest qurans around, in Birmingham or Samarkand, all date at least 200 years after mahomet, and all of them are grossly incomplete, missing numerous pages.