Hope that someone can answer my question 1) When someone say alpha transparencies what it mean ? 2) Does DirectDraw7 support anti-alias ?

1) Alpha transparencies are what you''d normally think of as "transluscency", often with variable values throughout the entire image (really see-through at one point, completely opaque at others for example).
2) No, unless you do it manually. All DirectDraw really does for you is copy and move memory chunks fast, as well as initialize the screen, etc. Everything else you have to do yourself. Have fun