Берёза is a poem by Sergei Esenin written in old-style Russian.
In 1917-8 in Russia it was carried out reform which made writing a bit easier, precisely some of letters were canceled out. For example, Ѣ, Ѳ, I all disappeared from the list. Letter Ѵ was replaced by И.
Fortunately, Ukrainian has been kept as it was. So we can see some difference between Russian and Ukrainian. It could be said that Ukraine is closer to Slavic language.
By the way, in Russian alphabet there are 33 letters and 42 sounds.