The volatile key word and memory consistency errors

Question

In the oracle Java documentation located here, the following is said:

Atomic actions cannot be interleaved, so they can be used without f

Answer 1

Ad 1: With a volatile variable, the variable is always checked against a master copy and all threads see a consistent state. But if you use that volatility variable in a non-atomic operation writing back the result (say a = f(a)) then you might still create a memory inconsistency. That's how I would understand the remark "reduces the risk". A volatile variable is consistent at the time of read, but you still might need to use a synchronize.

Ad 2: I don't know. But: If your definition of "happens before" includes the remark

This means that changes to a volatile variable are always visible to other threads. What's more, it also means that when a thread reads a volatile variable, it sees not just the latest change to the volatile, but also the side effects of the code that led up the change.

I would not dare to rely on any other property except that volatile ensures this. What else do you expect from it?!