Just learning DOM and EVENTS it seems like one can style a full webpage using only JS. Is it correct?

Answer 1

Yes correct. But you'll be doing extra work because you'll be writing JS and CSS.

Answer 2

Yes it is correct. But you'll make your code extra complex. In small projects, it'll be understandable but in large projects, it'll be hard to understand for you and others as well. And also you'll be doing some extra work by doing this.