jpeg export and contour inside options in illustrator

Hi everyone,

I used to work on corel draw but now i have started using illustrator. I have few questions please help me with it.

1) how to export selected objects only in jpeg format. How can i decide the size of jpeg in cms/inches etc.

2) how to use offset path in inside the object? like contour tool in corel draw allows us to make contours inside as well as outside. 

please share your experiences.

thanks