This is it. This is absolutely, definitely, finally Carlos Acosta's farewell to classical ballet. He has managed to spin out his retirement celebrations for almost a year: he gave his last performance on the Royal Opera House main stage last November, and there have already been two versions of the gala show which opened at the Royal Albert Hall last night, one at the Coliseum last autumn and a touring one during the spring and early summer of this year.

Why does Natalia Osipova, one of the world's best classical, dramatic ballerinas, want to start a sideline in contemporary dance in the middle of her career? Two years ago, when she mounted her first self-commissioned contemporary triple bill with her then newly-ex-fiancée Ivan Vasiliev, I was willing to believe that it was for the love of trying new things, pushing her own boundaries, and taking all aspects of her artform seriously.

In London, seeing the same ballet company do three different pieces in three different theatres over four nights would be some kind of festival. In Berlin, it's just business as usual – albeit quite a busy week! – for the hard-working Staatsballett.

One of the secrets to enjoying life is mastering the creative use of disappointment. Many in the Covent Garden audience last night were no doubt deeply disappointed not to be seeing Natalia Osipova's legendary portrayal of the title role in Giselle, injury having removed the Russian superstar from the opening night cast.

With its hybrid Romantic-kitschy plot, chocolate-advert Tchaikovksy tunes, and baggage of obligatory Christmas cheer, the Nutcracker is harder to get right than you might think if you've only ever seen Sir Peter Wright's Royal Ballet version, now over 30 years old and still practically perfect in every way.

With real live birds fluttering across the stage, and a sweetly happy ending – hurrah for young love! – Frederick Ashton's 1961 The Two Pigeons can look like mere frothy fantasy, precisely the kind of trivial, uncomplicated ballet plot that the young Kenneth MacMillan was reacting against in his own work in the early 60s. Is its return to the repertoire after an absence of 30 years just the Royal Ballet pandering to the escapist fantasies of its audiences – who, director Kevin O'Hare reveals, have been clamouring for this revival?

Swan Lakes are not created equal. In fact they are not even created the same: ballet is the art form with the evanescent repertoire, in which First Folios – or any folios – are singularly scarce. Even with a classic as beloved as Swan Lake, there is no stable text apart from Ivanov's lakeside choreography for Act II and Tchaikovsky's score (though not even all of that).

Wayne McGregor wasn't anyone's idea of a ballet man when he was appointed choreographer in residence at the Royal Ballet in 2007. Before then, and since, his work has been abstract, spiky, verging on dysmorphic. His interest lay not in human stories but in the snap of synapses and the speed with which the brain can relay messages to a hyper-flexible body.

If the Trocks didn't exist, we would have to invent them. Every genre needs its loving parodists, treading the fine line between homage and dommage, and an art form as stylised and convention-governed as classical dance is riper for it than most - as evidenced by the continuing worldwide success of this all-male comedy troupe after more than 40 years.

St Petersburg Ballet Theatre is a phenomenon of the new Russia: not anchored in centuries of history or state patronage like its neighbours the Mariinsky and the Mikhailovsky, but founded as a commercial venture in 1994 by Konstantin Tachkin, a wannabe impresario with no balletic training. It tours widely, and evidently has no difficulty selling out foreign theatres – including the Coliseum for Swan Lake last night – with a combination of recognisable productions and "Russian ballet" cachet.