I’m not sure you understand opening theory. It takes years to learn a single opening, and I don’t think any serious player would claim they know all variations/

I’m not sure you understand opening theory. It takes years to learn a single opening, and I don’t think any serious player would claim they know all variations/sidelines of a given opening. There’s no single “best” opening because you can always employ a defence for a specific opening. For example, there’s a trap against the London which is to play 1. d4 d5 2. Bf4 h5. 3. e3...