Christians, are all other religions outside of Christianity false religions?

Idolatry actually.


God hates religions. He sent his Son Jesus to put an end to religions, not to make yet another.


John 3:36 KJV — He that believeth on the Son hath everlasting life: and he that believeth not the Son shall not see life; but the wrath of God abideth on him.


See "idolaters"


Revelation 21:8 KJV — But the fearful, and unbelieving, and the abominable, and murderers, and whoremongers, and sorcerers, and idolaters, and all liars, shall have their part in the lake which burneth with fire and brimstone: which is the second death.

yes


Joh 14:6  Jesus said to him, “I am the way, and the truth, and the life. No one comes to the Father except through me. 

Not necessarily.  I expect most other religions, particularly Judaism or what Judaism used to be, have truth in them, too.

There have to be one truth.

Claiming exclusivity is not unique to Christianity.  Every religion, with the possible exceptions of Hinduism and Spiritualism, claim to be the truth.  Your question could be asked of any one of the world’s religions.

Everything which is outside of God's truth is falsehood, including that which is taught by denominational sects which are in disagreement with the words of God. It is not God's words that cause confusion, but the cults who cast off God's words, not believing all, but also adding to, and subtracting from them. 

I believe that is true with an exception because God shows in Daniel 11 a future sect of Jews in the Tribulation who are counted by God as faithful to him. Everything else is a false religion to me. 

Yes. Religion involves man trying to reach God or a better afterlife by doing good works. Religion cannot save you; only Jesus saves.

The truth is that death leads to heaven or hell, and the only way to heaven is through faith in Jesus Christ.

The Bible is very clear that no one can earn their way to heaven since good works do not pay for sins. See Gal. 2:16, Rom. 3:23-28, 4:4-5, Eph. 2:8-9, Tit. 3:5. The only way to heaven is by believing in Jesus for His free gift of eternal life. Jesus shed His blood on the cross as the full payment for our sins. He did all the work; all He requires of us is that we believe in Him. Once you believe in Jesus Christ to save you, you are secure forever!

Because we have all sinned against a perfectly holy and righteous God, we all deserve eternal separation from God in hell (Rom. 6:23). However, God loves us so much that He sent His only Son Jesus to die on the cross as our Substitute so we don't have to go to hell. Christ died for our sins, was buried, and rose from the grave three days later (1 Cor. 15:3-4). He gives eternal life freely to anyone who simply believes in Him for it. No one can be saved by doing good works. Salvation is by grace alone through faith alone in Christ alone (Eph. 2:8-9).

"Verily, verily, I say unto you, He that believeth on me hath everlasting life" (John 6:47).

What's the point of such a question?  If they thought another religion was true then they'd join that religion instead.