Do for learning html5, are we required to have a knowledge of html 1 2 3 and 4 versions

Answer 1

Nope, you do not.

Answer 2

Nope!....HTML5 contains latest tag which is certified as new latest standard . so you don't need learn earlier version

Answer 3

No!
Do you need Windows 98 to install Windows 10? ;)

Answer 4

Hi,
No, you don't have to learn the lower versions; as HTML5 contains almost every tag from older version and it provides new tags to enrich the multimedia contents like (Canvas,Video...)
Take a look to have some more clear idea @ https://www.w3.org/TR/html5-diff/