Absolutely. You may access your purchased designs at any time by logging in to your Account and clicking “Downloads”. There is no limit to how many times you can download each item.
By purchasing a file, this allows you're allowed to create 200 items and sell them. You MAY NOT sell the file/design, just the items you create. You MAY NOT share, give, or sell the actual files, even if you modify them. You MAY NOT upload files/images to “print on demand” sites such as Redbubble, Zazzle, Café Press, etc.
The file formats are SVG, DXF, EPS and PNG
You can open the purchases from So Fontsy on a variety of programs such as: Silhouette Studio, Cricut Design Space, Adobe Illustrator, and Corel Draw.