The undo option is a single state removal option. But what if you want to edit option from past, say 5 click ago. This is possible through history palette in photoshop. By default the history palette is shown in right side. if you can’t see history palette, follow this.
From…

Create a duplicate document in photoshop is very easy. Open the image you want to duplicate. Now follow this:
Image -> Duplicate

This is a new feature of photoshop. The save for web option allows you to optimize the files for size while seeing the results to quality.
Menu -> File -> Save for Web.
This opens a new window. In upper left, click on 4-up. The 4-up button is shown below.…

First Select the part of image which you want to copy. Selection of image part can be using marquee tool. The marquee tool allows you to click and drag an area of an image, thus selecting it. Select marquee tool. Marquee tool is show below.
Now select…

If you have messed tools setting in photoshop, than you can reset it to default setting. Click and hold the left area of the tool option bar. A window will pop-up and will show you two option. Select “reset all tools”. A popup will ask for conformation, click Ok.

To create a new document in photoshop follow these steps;

Open photoshop.
Click “File” in menu option, and than select “New”.

You see get a windows like this.