This is false. It is true that the church teaches that you can be saved without going through the church, but this does not apply if you are aware of the church. Invincible ignorance does not apply to those who are not ignorant.

I believe the main issue is whether one refused god or not (i.e. catholic who renounced the faith). Being aware of faith but not practicing while still fulfilling the requirements does count, iirc.

No, I'm pretty sure it doesn't. I mean, this is one of the mayor schisms between Protestant and Christian churches.

You can check the catechism if you want. It puts it in black on white.

Not really. If you are, muslim yes. But if you are Catholic, then one of your duties is mass every Sunday and not doing so is a mortal sin.

There are diverging views on the subject. For some, it suffices to act according to what Jesus taught. For others, the more strict observation of rituals is a necessity.