Flippanarchy

1. As long as we both understand.

2. The idea that Marxists and Anarchists have the same end goal is common of those who don't read Marxist theory. Marxists and Anarchists have a different notion of what constitutes a state. Marxists see States as the aspects of society that enforce class oppression, Anarchists see States as monopolies on violence and hierarchy. As a consequence, Communism for Marxists is a world Socialist Republic fully Publicly Owned and Centrally Planned, as classes cease to exist in such a system, while for Anarchists Communism looks like a horizontal spiderweb of mutual aid networks. This fundamental difference in end goal means the tactics are different as well.

Marxists don't have a monopoly on "Dual Power," no, but those using the term "Dual Power" are almost always Marxists. I'm not saying that Anarchists don't practice similar approaches, but that calling said approach "Dual Power" has a Marxist connotation. Again, this is more semantics.

As for unification of Means and Ends, Anarchists place more importance on it but Marxists don't abandon that either. Engels does a good job of explaining the whithering away of the State:

When ultimately it [Cowbee clarification: The State] becomes the real representative of the whole of society, it renders itself superfluous. As soon as there is no social class to be held in subjection any longer, as soon as class domination and the struggle for individual existence based on the anarchy of production existing up to now are eliminated together with the collisions and excesses arising from them, there is nothing more to repress, nothing necessitating a special repressive force, a state. The first act in which the state really comes forward as the representative of the whole of society -- the taking possession of the means of production in the name of society -- is at the same time its last independent act as a state. The interference of the state power in social relations becomes superfluous in one sphere after another, and then dies away of itself. The government of persons is replaced by the administration of things and the direction of the processes of production. The state is not "abolished", it withers away.

The Socialist government that forms the basis of Communism gradually folds Private Property as it develops into monopolist syndicates and makes itself ripe for central planning, this is why Marxists claim the State cannot be abolished overnight.

Question 17 : Will it be possible to abolish private property at one stroke?

Answer : No, no more than the existing productive forces can at one stroke be multiplied to the extent necessary for the creation of a communal society. Hence, the proletarian revolution, which in all probability is approaching, will be able gradually to transform existing society and abolish private property only when the necessary means of production have been created in sufficient quantity.

I'm not trying to argue against Anarchism here, or even argue in general, just offer clarification on Marxism. This community has strict rules against supporting Marxist movements and opposing Anarchism anyways, and I don't wish to infringe on those rules, but there's nothing against clarifying the Marxist stance.