Microeconomics question
Your first answer would be correct conceptually if this was an interior solution. (The math is incorrect because 2*0.9=1.8 and not 0.18).
However, note that the price falls below the average variable cost. So the firm is better off not producing at all both in the short and long term.
As for your second question: you confuse revenue with profit. Revenue is $p*q$, profit is $p*q-c(q)$
For good measure here are two graphs: one depicts profit for q=0 to 20. Clearly it's negative for the full range 
And here's one depicting average variable costs which you can see never falls below 4.