What is the hardest and easiest to learn opening on chess.com?

Sicilian :Hard :: ______:Easy

There is no clear cut answer. The Sicilian isn't necessarily the hardest. It depends on how the brain thinks.

There are 5 types of pawn center. Closed/Blocked, Mobile, Static, Open, and Dynamic.

Everyone has their comfort zones (Closed, Static, Open), ones they are ok with (Dynamic), and weak spots (Mobile).

The fact that my issue is understanding the Mobile Center, where you have "Sicilian", for me would be "Grunfeld", and for someone else would be, say, French (if they don't understand closed positions) or Berlin (if they don't understand open endgame positions), etc.

So for me, the Petroff is easy. For someone else, the Sicilian Dragon is easy.

Actually, if you REALLY want easy in my case - the Black side of the Exchange French is easy. In Symmetrical positions, it is Black who decides when symmetry is broken and how long he plays the copycat game.

Grunfeld and Scandanavian (in that order) are generally considered the hardest and easiest defences to learn.

For the easiest opening against d4 maybe the Albin Countergambit and the hardest opening against e4 to learn I'll say the Sveshnikov - many complexities and quite dangerous.

For the white side it's harder to say what hardest and easiest mean, because white is trying to prove an advantage. White does something and black responds is normally how the opening goes, so you can divide black's openings into simple and clear vs audacious more easily. The London System is probably easiest to learn. The King's Gambit is then likely the hardest. Of course the king's gambit is now considered unsound to play at all against really good players (>2300), but works fine against lower rated players, you just have a lot of work to do in it. The Scotch also excluding gambit stuff is a very complicated and hard opening to learn.

I am going to reveal the Secret of easiest line.

Beginners around the World have been playing the Caro-Kan!

Oh, Yeah - The Secret is out!

The Caro-Kan is so easy and fun to play.