can i delete a application extension without messing any thing up?

Answer 1

It actually depends on the extension. If it's an extension you know you don't use / want, then I say by all means, go for it. However, don't do so unless you know exactly what you're doing.

Answer 2

As a rule...no. The extension is what the OS looks for in order to associate an application with the proper software i.e. a .doc extention refers to MS Word and then Windows knows to boot the software to open it. I would highly reccomend NOT deleting extentions.