yes
The newest edition of iMovie for the Mac, allows you to stabalize a video.
Video editing
The video editing software suite Final Cut Express was created by Apple, Inc and released in 2003. It was discontinued in 2011 and replaced by Final Cut Pro X.
Final cut pro X
final cut pro
They use Final Cut Pro 7.
Apple's Final Cut Pro video editing software is part of the Final Cut Studio suite. It costs $999 (£816) and is not legally available for free.
The best and simplest video editing software is probably Adobe Premiere, which is cheaper than Avid and Final Cut Pro, but still powerful.
To cut a video using Final Cut Pro, import your video into the software, place it on the timeline, and use the blade tool to cut the video at the desired points. You can then delete or rearrange the clips as needed to create your edited video.
Yes there is FLV Player that allows you to play any flash video file
Final Cut Express is video editing software and iStopmotion is stop motion animation creation software. They do not work together but as they both use the standard QuickTime formats you can export your video from iStopmotion in a format suitable for importing into Final Cut Express.
There is a lot of companies that make video studio software but Final Cut Pro is a popular video editing program for the Mac. Split screen is relatively simple to achieve in Final Cut. Select two pieces of footage to use for a split screen and make sure they are the same duration.