How to make step to step on my site

I make content locker on page load, insert code to an empty page and use Iframe with the link to that page.
I want to make a function like

Like you see, the page has 4 step to get gift code. The content of step 2 only shows when step 1 is completed, same with step 3 and 4.
So I want to know how to do that
( And in step 2 has offers people need to do, how do I know when people finished the offers and step 3 show content to them)
Can You have look that site and give me some advice. ( I'm noob so you guy can suggest me and I will research more)
Very appreciate.

That looks abit like typeform. Its a form plugin that you can use to make interactive forms. At the end of the form you can link to your content if you wish. Its free for the basic features, and expensive for all features but still worth it

You can do it easy with javascript.