Before and After Food

2 people made hamotzi, one said shir hamaalot and wants to make a zimmun, could a third person eat now and answer the mezuman?

My rabbi says the blessing over wine at Kiddush every Shabbat morning. However, he does not drink the wine. Is that proper?

Hello I make myself a juice in the morning and it has a mix of fruits/vegetables. Which blessing do I do before drinking it? (apples, celery, beets, green leaves, carrots etc)

Prayer before drinking water: If I have a water bottle I take with me throughout the day, do I do the blessing once? Or do I do the blessing every time before I drink? Thank you!

There is gluten free bread on the market that looks and tastes just like regular bread and the bracha is shehakol. Is a person who does not require a special gluten free diet permitted to use this bread to dodge washing hands and benching when doing so is inconvenient?

If I forget to say a bracha before I begin eating an item, and then suddenly remember, can I say the bracha even though I have already started eating it? I vaguely remember that I cannot say it after the fact, that I've missed the opportunity. What is correct? To say it late, or not to say it? Thanks!

Would you please send it to me, I can not find it. Thank you, Debbie Duncan