Play from the start?

My entire project completely runs on frame 1 in stage 1. After 30 seconds i want to put a button that says Replay. What do i need to do for it to start playing again from the start?

First you will need a timer and after 30 seconds you will need to add/create the button.
On click on that button you will need to do call again the methods that you also called initially.

How do i call the methods that i called initially? Is this via action script?

If you used action script until there, then yes(you can find the list of flasheff methods and description in the action script usage manual from the component's package). If you used timeline then just use the timeline and insert the number of frames needed.