I want to use bone tools without change the shape of circles. but when using selection tools,
square changes in this way:
how can I disable this effect?
I think you could try parenting/grouping the small one to the medium, the medium to the large. Then you can go 'inside' the bigger ones and move the smaller ones relatively. It's a bit clunkier than having inverse kinematics, but it'll do just what you want.
Besides Flash, this should also work in other software like Illustrator or LibreOffice Draw.