What is the alternate option for Print screen key

You could use the Snipping tool feature which is available in Windows OS 8 and 8.1. You can either use the full screen snip type if you wish to capture the entire page on your screen, or the rectangular snip type if you wish to capture only a specific part of that page. Once captured, you can then save the image on your computer.

You can download small utility tool known as Sharpkey. With this tool you can easily Map any other useless key on your keypad as your desired key.

Download Link Of Sharpkeys
http://goo.gl/rt1EQg

If you are using Windows 8, then Snipping tool is the best and easiest option out there. But if you are using earlier versions of Windows like XP and 7. Then youu should use Jing.

Jing is a free service from TechSmith (creator of Camtasia). The interface is fun (a small 'sun' at the top corner or top center of your screen) and easy to use. In addition to capturing screenshots (PNG files), Jing also allows a user to take a five minute or less video, including sound, of their screen; the video can then be saved to one's computer as a SWF file and/or saved to and shared online at TechSmith's Screencast.com for free.

I would suggest you to use the On Screen Keyboard available on Windows. If your physical keyboard has stuck up keys or broken, the on screen keyboard should be the best option for you to explore.
In the Run command, type in "osk" and your on screen keyboard should pop up. You may also resize it so that it will not hamper your view.
If your On screen keyboard does not pop up , use search feature to find it.