Full-sized Landing Page with SCSS

1. How far do people actually test the responsiveness of a website (the smallest width it can be, weird aspect ratios, etc.)?

2. A bit off-topic I guess: How long and how deep did you study programming before you consider yourself competent? I find it hard to gauge how far I'm right now, not to mention I have been jumping between languages (sometimes its because I lose interest, other times life just happens I guess),

Thank you for looking at my solution and answering my questions!