In Act I, Ariel and Erica come to cottage. There are green deciduous shrubs in the front of cottage but they are snow sprayed. There are even green deciduous trees but they are carefully blurred, and you can see them again when Ariel and Mark go out of cottage a bit later or when Ariel's family comes. Around half of movie, Peter, Duke, Trevor and Jasmine go through forest, and you can see again snow sprayed deciduous trees. But the worst offender was at around 1:10 in when Ariel and Mark were sitting back in the backyard in the evening. Somebody forgot to snow spray - there was barely any snow on the ground, and you can see a lot of beautiful light green / a bit of yellow vines plants.
Mark Henderson had flight to Australia two weeks after New Year, but it was pushed right after Christmas. This was one of the major issues in the movie. However, Australia closed its borders since March 2020, and only reopened on the 21st of February 2022, so no, Mark couldn't fly to Australia at all.