The basic answer is - you can rerender a project as many times as you like.
First suggestion - load the project then delete the auxiliary files (careful, not projects), switch to the time line mode and try rendering again.
Second suggestion - if the render hangs, note where in the time line the cursor has stopped. Abort the render and then look at that area of the time line for gaps. You may have to expand it to frame level granularity to be able to see it.
How to cut and paste - switch to the time line mode and click in the time line. Press control A to select the entire project then control C to copy it. Now open a new project, click in the time line and press control P to paste it in. Warning, when I have done this in the past it has resulted in time shifts which required some adjusting.
Let us know how it comes out.
Jerry