Download literally any version of Flash and fuck with it. Actionscript is how you program buttons and the like. It really isn't hard, if you don't feel like learning the concept of the code just copy and paste other people's work. I used actionscript in Flash 5-7. From what i hear the newer versions are a LOT easier as far as simple buttons and shit goes.
I mean i used flash 5 when i was 10-12 pretty heavily. Made some small games, decompiled other games and modified them (like madness interactive... that was a nightmare to figure out but i eventually did).
Frame by frame animation is very easy, think of it is a flipbook. Onion skinning is your friend. Traditional anime works like this, Yeah GALO SENGEN.
Shape/motion "tweening" is where you find the ultra smooth animations that some flashes have. You basically draw an image at point A, then move the image X amount of distance over X amount of frames and flash will move it for you accounting for rotation and scale (think minus8 or whoever does that porn shit, most of that is motion tweening a ton of shapes in unison to make it look like a fully moving object) Shape tweening will attempt to turn your vector image into another vector image over an amount of frames. I dont know if it even does shape tweening anymore or if it is of any value. It is usually really shit. I used this program 10 years ago.
As far as ripping shitty videos and importing them into flash i know fuck all about it. I just know if you do don't make it trash or i will be mad. For a board called flash a lot of people just post youtube flv rips now. If you make even the most basic like 50 frame animation or some stupid button adventure game i will be hella psyched. Good luck. If i did what i did at 10 years old you can do it now. I'm too fried for flash OC these days.