Determine whether a given function is a pseudorandom generator/function
I have fully solved the questions now.


Not a pseudorandom generator since the first bit of $G(s)$ is always equal to the XOR of the second and third bit, i.e. a distinguisher can easily tell $G(s)$ apart from a truly random string $r$.
Not a pseudorandom generator. We can for example construct a distinguisher $D$ that, on input of a string $w$, outputs 1 if and only if the final bit is 0. If $w$ is uniformly distributed then the final bit is 0 with probability $\frac{1}{2}$ but if $w = G(s)$ for a uniformly distributed seed s  the final bit will be 0 with probability $\frac{1}{4}$.
Not a pseudorandom function. A distinguisher D could tell $F_k$ apart from a truly random function $f$ in the following way: Given access to an oracle $W$, D queries $W(0...0)$. If $W = F_k$ then the result will always be 0, but if $W$ is a random function then it should be 0 only with probability $\frac{1}{2}$.