can I use two or more attributes to a single subject?

Answer 1

You shouldn't use attributes to control layout or style like 'align'.. For that, you should use CSS. Other than that, you're allowed to use as many valid attributes as needed. Example:
<a class="btn" href="#">Home </a>

Answer 2

Yes..As many as you need to describe the tag. For example <p class="top p" align="center" style="font-family: Arial;"> </p>

Answer 3

yes...you are allowed to do so

Answer 4

yeah ofc y not!