Developing a Visual Studio Extension for VS 2005+

I am developing a Visual Studio Extension the I would like to be compatible with VS 2005+(2005,2008,2010,2012,2013 and eventually 2015).

I have been looking into the requirements for this to be possible and came across this Manual on doing it http://www.viva64.com/en/a/0082/ .It covers a lot of the details on how to accomplish this, but I am lost when starting from scratch developing my first VS extension.

The Article says,

developing VS extension packages requires the installation of Microsoft Visual Studio SDK for a targeted version of IDE, i.e. a separate SDK should be installed with every version of Visual Studio for which an extension is being developed.

Does that mean I need the 2005 SDK, 2008 SDK, 2010 SDK, etc.?

Also, I don't see anything about what version of Visual Studio has to be used. I found some other articles that mentioned versions, but they were related to 2010+ extensions.

I am assuming I should use the .NET framework 3.5 for backwards compatibility.

I have the following questions:

1. What version of Visual Studio I should create my project on?
2. What version of the .NET framework I should target?
3. What Visual Studio SDKs will be required?