Answer 1

i'd recommend gsap (JS) which is much faster and more efficient and then css
https://greensock.com/gsap/

and here is a comparison
https://css-tricks.com/comparison-animation-technologies/

happy coding

Answer 2

JS, Java etc.

Answer 3

In html you can use css3 or javascript(in tag canvas) animation

Answer 4

CSS

Answer 5

CSS .
But I prefer JavaScript

Answer 6

CSS is pretty good for animations.