Is Bitcoin for speculation only?

Answer: Yes Bitcoin was started in speculation only were some of the business minded people adopted it and control the value of it in my own
             perception only.

Is it really useful in our daily life?

Answer: If I'm gonna compared it into my life before at the present time now, yes it was very useful to me since 2015 up to now I am not
             employed but a a jobless individuals but still earnings Bitcoin or cryptocurrency as my own personal source of income for a couple of
             years now.

What product can we buy by using bitcoin only?

Answer: There are a lot of merchants all over the world now accepting Bitcoin as their mode of payment in different countries as well.

how many Merchant accepting bitcoin?

Answer: No idea dude, but in my estimate count I think it almost a thousands merchants now, not so sure but it could be more or less.