Mac Newbie here...

That is normally true. Some small files may be left behind, but they won't cause any damage or slow down.
Uninstalling Applications in Mac OS X

which also includes:

Best way to FULLY DELETE a program​

 

Basically yes (pretty weird for people coming from Windows!) but you might want to completely uninstall it and remove everything about this app - http://guides.macrumors.com/Uninstalling_Applications_in_Mac_OS_X

 

Mostly, yes. But not always.

In fact you don't even need to drag to the trash in OS X Lion, just like in iOS you can click and hold an app in Launchpad to get little crosses next to each app, from there you can delete the ones you no longer want.

 

This may also be useful: Helpful Information for Any Mac User

Also, you may have better success in attracting responses to your thread, and you'll make your thread easier to find for those browsing the forum for the same answers, if you follow this tip.