4. When are exclusive Scottish country dances steps became known?
There are no exclusive Scottish country dance steps. At a social dance/wedding/party it's OK to dance Scottish country dances with any step that fits the music. Among those taught by the RSCDS you do see a similarity about the steps used, but also individual and regional variation. I am sure that in certain parts of Scotland, certain stepping styles were customarily adopted, and may look different, but are basically similar in pattern and rhythm to those in the rest of Europe. For example, the reeling and setting steps of the Shetland Isles resemble those in other parts of Scotland, but there are distinctive features about them. Even today there are strong regional variations, particularly among the dances done at weddings and parties. Standardisation was something the RSCDS was enthusiastic about and their strathspey step is particularly distinctive, as are some of the formations in their published dances. I suppose you could conclude that RSCDS dancing is equivalent to Scottish Country Dancing these days in terms of its distinctive style compared with other types of set dancing in the UK.