The game will be in Russian when you start it. (If you need) Use this guide to change the language to English:
http://steamproxy.net/sharedfiles/filedetails/?id=849701741
Then proceed with my guide.

Forever Young
Go down to Ulyana.
Stay and launch the fireworks


Elevator to Heaven
Go down to Ulyana.
Go get a warm.


Star of Stage
Drop down the firecrackers from the window.
Stay


Deja Vu
Drop down the firecrackers from the window.
Come.
Look at Slavya.

Gift
Drop down the firecrackers from the window.
Come.
Look at Lena.

Well celebrated!

You get this cheevo after completing all 5 endings.

Special thanks to my motivation and inspiration - this person

Thanks for being an awesome friend! <3