Not ''snaping''it just...happens?at least from our perspective

You can do anything with it. Since you can manipulate cause and effect, you can basically induce any effect you want without the need of the cause. But if you want, you can still make a "cause". For example: Effect = universe gets destroyed, Cause = saying "boom". So if you say "boom", the universe will get destroyed

In regards to immortality, basically yes. The user completely negates any undesired causal relations and can make it systematically impossible for any cause to bring an effect that would end them. And when it comes to what they can do, pretty much anything, really. As @Abdalla1234 said, they can induce any desired effect without a rational cause or just assign their desired effect to a cause.

@AzQth I see. Can someone with Causality Manipulation can walk into a black hole, unaffected, explore, and then leave to go somewhere else, like a metaphysical plane? I'm trying to understand what all kinds of effects can be induced. You could grant yourself infinite strength, erase a being from existence, manipulate something, get smarter, make magic, psionics, and other abilities do whatever you want? Sorry for all of these questions. 😅

@Necropolis00 Yes it would allow all that because it allows anything.

@Ogtea True.

Exactly as @Ogtea said, Absolute-level Causality Manipulation can generate any effect, regardless of the factors such as laws, logic, reality, etc. In this sense, it can accomplish anything it wants in any way it wants (since any effect can be generated through any method, or through no real method at all).

@AzQth How do you stop a being with this power assuming that they are not the Omnipotent?

You need to either have an omnipotent power or have a power that can kill/erase/etc absolutely and instantly and hope against hope that their power doesn't have a passive aspect and at the same time that they've been stupid enough not to either give their power a passive aspect or make it impossible for anything to cause an unwanted state of being for them (or something along those lines). Sub-powers of Causality Manipulation such as Acausality and Causality Negation, taken to absolute levels, should render them immune to all opposition, so if those sub-powers are correct, then you would need omnipotent-level powers to defeat them for certain.