Quote:As per my assumption it allows A-Z, a-z ,0-9 and spacial characters like Back slash,
Single Quote, and Hyphen.
Your RegEx is a little more complex than that, looks like your problem is that you use RegEx without really learning it.
Use last link and paste the RegEx and you will see a nice graph of your RegEx, hope it helps you to understand it.
Just a few interesting links to help building and debugging RegEx.
Here is a link to RegEx documentation:
perlre - perldoc.perl.org
Here is links to tools to help build RegEx and debug them:
.NET Regex Tester - Regex Storm
Expresso Regular Expression Tool
This one show you the RegEx as a nice graph which is really helpful to understand what is doing a RegEx: