TLDR: You reply by saying "duly noted" when you have understood what someone has just told you and will consider that option/piece of advice.

TLDR: it's 'grammatically' correct, but it just sounds dumb.

TLDR: A pint and a quart are both units of liquid measurement used in the US and the UK, but they represent different amounts. Understanding the difference between them is useful when cooking, shopping for beverages, or handling liquids.

"Hi how ya doin'" may sound like a question though, more like an affirmation. Do you expect us to answer that or is it just pro forma as a conversation starter?

Titles can be good alternatives to those gendered terms. So if you're writing a potential employer use "dear hiring committee/team" or "dear hiring manager". There's also "to whom it may concern" but may be too formal/cold depending on the scenario.