According to Dr. Zakir Naik, if you are a True Christian, then you can still go to Jannah. And to be a true Christian, you have to meet some conditions:
You have to believe in one God (no trinity)
You have to follow the teachings of Jesus (pbuh)
You have to acknowledge Muhammad (pbuh) as the final messenger
Unfortunately, such Christians don't exist anymore. But what if they did? What if I was a christian who met all the conditions mentioned above? There are still 3 problems:
I can't pray salah because only muslims can pray salah. So how should I pray?
I can't read the bible because the bible is corrupt. So which scripture should I read?
I can't read the Quran because you have to be a muslim to read the Arabic version of the Quran. I can only read the translated text but they don't have any divinity in them. So how should I read the Quran?
So the point of this question is: If the proper way of worship is limited to muslims, then how can True Christians worship Allah? Do they have to learn Hebrew and pray like the Jews?
And just as a side note, I'm a muslim, not a christian. I was just using an example to make the question easier to understand