11) How can one read parameter values through the URL in Apex.

Hi,

If you have ID parameter in the  URL then try this apex code.

public Id oppid{get;set;}
Id id = apexpages.currentpage().getparameters().get('id');

If you want to read parameter in Visualforce the write in 

visualforce page :

<apex:inputField value="{!$CurrentPage.parameters.Paramtervalue}"/>

If you have to add a parameter to the URL the use

ApexPages.currentPage().getParameters().put(parameterName , value);