Identifying Cap Badges

There are four badges here and I have absolutely no information on any of them, so any info anyone can give me would be greatly appreciated. They were found at the Blenheim Freedom Library and Military Museum in Ontario, Canada.

Hi The badges are, from top to bottom, the 12 Battalion Canadian Expeditionary Force, The Scots Guards (British army), Canadian Army Dental Corps, and Le Régiment de Montmagny. The CADC badge dates circa 1929 through 1947, and the R de Mont was authorized 1928, and the unit was amalgamated with the Fusiliers St Laurent in 1954.

Thank you very much!