I have a trial copy of Video Easy 4 HD, registered on 20th January 2013, I can't find how to raise a question regarding apparent problems with the software.
This is probably the place to start. While we are a user community and none of us works for Magix, there is an incredible amount of knowledge and experience here. Try asking your questions on this forum and if we can't answer them, we will point you back to Magix sales or support depending on the question.
1. When editing the colour of a scene the use of the 'Exposure' or 'Color' button together with a saturation adjustment, causes playback to be jerky.
2. When the 'Reset' button is used, scene recognition seems to be lost for that scene - the beginning and end markers close up as though the screen represents the whole project rather than just the scene.
What is the spec of your computer - depending on the spec and if you are working with HD video, then the jerkiness is quite likely as there is a lot of image processing going on during playback and there may be very little you can do about it - it does not affect the final video.
. . . .the 'Reset' button is used . . .
That is correct according to the manual: 'It disables all applied effects' - ie the clip is set back to its original state when imported, including any scene recognition.