I am a beginner and still, i am not familiar with this. Can I make an animation in Adobe Flash and import it as an asset in my game to serve as my game’s splashscreen? If so, can you teach me how and if not, can you suggest oither ways to do my splash screen? Thanks. 
Custom splash screens are a pro feature (doc).
However, even if you have Unity Pro, you can only set a static image to be your splash screen. A common workaround is to create an “intro” scene which plays a Movie Texture, and then loads your in-game menu.