Measuring time complexity of algorithm
For 1, suppose that $n = 2^{m+\delta}$, where $m$ is an integer and $\delta \in [0,1)$, and compute how many iterations the loop has.

For 2, it's easy to see that it's $\Theta(n^3)$.

For 3, the "inner" loop is $\Theta(n^2)$. Now suppose that $n = 2^{m+\delta}$ and follow the same procedure as in 1. (For starters, you might want to assume that $\delta = 0$.) You will get $\Theta$ of
$$ n^2 + \frac{n^2}{4} + \frac{n^2}{16} + \cdots = \Theta(n^2). $$