I have an eCommerce HTML template with simple CSS. I have a few queries before converting HTML into Magento 2.3.3

**Question 1:** Is a .less file is mandatory? Can we use a simple CSS file in Magento 2?

**Question 2:** I don't want to @import variable & import Less file in another Less file. So Could someone, please tell me the better approach to use HTML Template/CSS

**Question 3:** Why Magento 2.x use Less CSS? I have worked in Magento 1.9 there is no concept of Less & it uses simple CSS & that was very easy to change the color scheme of page design.

This is my first question in the Magento stack community, Hope someone will give a pertinent answer. Thanks in advance :)

**Updated Question on 13 Oct 2020**

How to convert CSS into Less if the project has using CSS?