These answers are from my 10 years of experience and heavily viased, but here goes.
1: what advantages/disadvantages does this script language have?
Extremely simple to handle window controls E.G. edit control, list box and other *supported* parts
Has powerful libraries (3D physics, 3D graphic, networking, database, mathematical, regular expression, and even the compiler engine itself)
Is able to syncronize with C/C++ dlls and COM controls
Does not support Windows's native character code (UTF-16, also known as wide chars)
does not support dynamic arrays (precisely it does, but ridiculously slow).
Does not support dictionary
Does not support callback function
Does not support object-oriented theory
Does not support float (Only double is available in script)
All variables are global
Has a namespacing feature, but it's buggy
Extremely hard to implement non-supported window widgets such as radiobuttons or tab sheets
String processing is very slow
It's cross platform, but there are some limitations meaning that it cannot perform everything that it can on Windows
Reference and all associated resources are in Japanese (Not a problem for me because I'm a native speaker though).
2: does this thing support dll?
Absolutely it does, but callback functions cannot be used.
3: does this thing support physics system?
4: does this thing support jason handling and stuff?
Yes, but the API is somewhat complicated.
I don't speak as good as I write, and I don't listen as good as I speak.