I make a link. A link is a link. A link navigates to another page. That is what links are for and everybody understands that. So Method 3 is the only correct method in my book.
I wouldn't want my link to look like a button at all, and when I do, I still think functionality is more important than looks.
Buttons are less accessible, not only due to the need of Javascript, but also because tools for the visually impaired may not understand this Javascript enhanced button well.
Method 4 would work as well, but it is more a trick than a real functionality. You abuse a form to post 'nothing' to this other page. It's not clean.