1. Though I don't think you finished your question, I assume what you meant is 'will the sound of someone telling you you're dreaming filter into your dream?', which is something I've never thought of but seems worth a try. When I was younger my recurring nightmare would be initiated by the sound of my parents walking up the stairs to bed (in my dream it was the monster), so external stimuli definitely have the capacity to seep into your dreams.

2. I assume it will be different for each individual. It could subconsciously distract you from your goal, or it could influence your dreams and make them more vivid.

3. Anything is possible in a lucid dream.

4. Reading about peoples' experiences will no doubt inspire some of your own, and give you ideas for dream subject matter, as well as reminding you to perform reality checks and other lucidity techniques.