So it's actually easy to downgrade to 4.1.5.

In order to download haxe you need to run several commands, one of which is
sudo apt-get install haxe -y

And for downgrading you just need to type a version after "haxe" like that
sudo apt-get install haxe 4.1.5 -y

BUT after installing additional libraries (haxelib run lime setup flixel) there is this error:
Error: Could not find haxelib "lime", does it need to be installed?

You can fix by downgrading lime, but when you install flixel-tools it's another error.

Should i just wait until flixel supports haxe 4.2.0 or there is a chance to fix it?

I am having the same issue as here http://forum.haxeflixel.com/topic/1191/haxeflixel-base-template-build-fails-and-generates-a-variety-of-errors.
And i can't find a way to install haxe 4.1.5 instead of 4.2.0 on linux.