A trouble in modelling snowman

[micheus]

But for this model it doesn't work (or I wasn't able to do it). It seems this model is kinda unfixable...

"Unfixable" for sure! You did something almost impossible.

I tried to "unfold" it and it's not easy to imagine how did you reach it:

In the bottom row, after I select the bottom face, it was a sequence of: move down; increase selection; Take a look at the 3rd and 4th frame and how the selection mix bottom and vertical faces.

Don't do that again.