True. The Catholic Church affirms this teaching. See the Catechism of the Catholic Church, paragraphs 817 and 846-848.
I’m afraid not. No one is saved by walking through any door, Catholic or otherwise.

As to Catholics believing that all other “doors” are the “wrong ones,” see the cited CCC paragraphs cited above.
It is always possible to walk out a door that is always open, and the door to the Catholic Church is just that. Everyone’s salvation is dependent on being in the state of saving grace–and that is not limited to the Catholic Church, as the Church herself teaches.
It is the mark St. Paul talked about:
Eph.1[13] In him you also, who have heard the word of truth, the gospel of your salvation, and have believed in him, were sealed with the promised Holy Spirit,
Eph.4[30] And do not grieve the Holy Spirit of God, in whom you were sealed for the day of redemption.
The Holy Spirit seals us against the “day of redemption” and gives us the power to obtain and retain God’s saving graces. It’s up to us to take advantage of those graces and grow in holiness. Thus, anyone can lose his salvation by mortally sinning and thus cutting himself off from the love of God, his grace, and the Holy Spirit’s seal upon our souls.
Certainly such a person can be damned. See my last answer above.
You ask questions assuming you know the answers, but you don’t, my friend. You cannot possibly know what millions of Catholics are doing by participating in the sacraments, which are not empty rituals but the means of saving graces.
You may want to research Catholic teachings before telling Catholics that their practices are useless and mean nothing whether or not they are practiced, don’t you?
Indeed. Me too.