Is it possible to escape the Yeti in SkiFree? I heard that pressing F makes you go faster, but fast enough?
According to this article, yes.
It is possible to escape the Snow Monster by traveling another 2000 m from the point which the monster gives chase, creating a loop and starting over from the beginning. One way to evade the monster is to go directly left or right in fast mode. He is right behind you, but cannot catch you unless you hit an obstacle. Pressing "F" can make you move faster than the monster.
Also, here's a video that shows it