I have the PC version, I have the prequel and all dresses/weapons, Apparently the PC version comes with it already as the console has a free DLC of the prequel, Retail PC version will have the DLC for free, the prequel, don't know about how they will handle the weapons and dresses issue but I think they will gie it for free, the sales already hit very high, only in my store we had to order 20 copies more cuz we ran out of it already. And we had 30 copies

Yes, it is safe to play AMR before playing AMA, although I highly recommend playing AMA first, even though you don't loose much of a plot not doing so, but you will have more understanding about what Alice talks about sometimes with the Hatter, the Cheshire Cat, and even with the Queen.