We can also use <li> tag without closing it.

Question

<ol>
<li>HTML
<li>CSS
</ol>
This will also work

Answer 1

ya it will work.. html is just markup language it does not have strict rules.. but working using improper semantics the browser will face problem and then the search engines to locate your data properly.. since every tag has its meaning..
like if you create a header with h2 and you increased its size to that of h1..
the browsers will understand it as h2 only.. it doesn't matter what styling you have done to it..
the same way it goes for unclosed elements.. if you don't close them browser will definitely show the content but will problem to interpret it

Answer 2

It will work but it's not valid HTML anymore.

Answer 3

okkkkkkk