What opening advice would you give to a beginner?

1. Try to control the central squares e4, d4, e5 & d5.

2. Try to develop all of your knights and bishops to active squares.

3. Try to castle your king early to safety.

4. Try to bring your rooks to open or semi-open files.

5. Try to avoid at all costs losing material.

6. Don't be too concerned with theory or particular opening lines - you have to learn how to play to a reasonable level first.

Blunders decide most games. So learn what all the checkmates look like, learn basic tactics. Play rapid so you have time to think 10+3 so increment can help you. Just do a blunder check before moving. (If the other player makes a move what can they do that would be really bad for me?) You might not get all of them, but you should make fewer than most beginers if you take the time to do that.

What do you recommend most to improve your level? Regardless of whether you're a beginner, intermediate, or advanced?

Don't be afraid of unusual moves, if you lose, you'll do it in style.

Don't worry about them. Play what comes naturally. Focus on tactical exercises, positional exercises with special reference to Pawn structure, and endgames. Why do I say this, you ask. In the mid 1990s I was some good at this game, now I'm just okay as a player. Looking at my games, it's not the opening that's letting me down (I am playing sans openings) but my lack of middlegame and endgame acuity after a 25 year layoff and an age-related loss of sharpness.