Dear Santhosh, First of all,IMHO,you shouldn't rush, have patience.
Using Qt you can easily run your application on many platforms. Here is the "List":http://doc.qt.digia.com/qtcreator/creator-os-supported-platforms.html#target-platforms. Which means, you can compile your source in Qt with no [ or less ] change.
You can Compile the source code using QMake on terminal or Your Qt-Creator will take care.
Once you go through "how to create a Qt project":http://doc.qt.digia.com/qtcreator-snapshot/creator-project-creating.html, you'll get answer for 3rd question.