“The piece is from '85,” says American critic and Ilya Kabakov expert Amei Wallach. “No, no, it's from '86,” retorts Joseph Backstein, Kabakov's old friend. Both of them should know, but here in the artist's former studiowhere the classic work 16 Strings has been reconstructedall straightforward facts seem to disappear into a thick cloud of Slavic mythology. It's January 30, the day after the opening of Moscow's first contemporary art biennale, and the curators, artists, and critics in town for the show have come here to pay homage. Kabakov built the studio himself in 1968 and lived