HTML, CSS and JS for submitting the form

Hi, I still have some questions after this challenge

• I was trying to use the BEM methodology but i'm not sure if I used it right
• Is there a better way of showing the selected radio button using javascript
• When submitting the form and showing the other element, is there another way of doing this instead of just adding and removing a class using javascript?

Thank you in advance for taking time to review my code