Autodesk InfraWorks

[#1]

There are two projects are the same, but one is stylized. How to move a style to another project and apply to all objects?

[#2]

Not sure if this is exactly what you are looking for, but if you have a style that you like, it is stored in \Infrastructure Models\<modelname>\styles\Defs\Street (for example).  You can copy a style out from there to a different model and then apply.

[#3]

Yes, it is, but a lot of styles and manually assign them long