In Footnote 1, I would have expected $q\left(y|x\right)=N(x^2,{0.15}^2)$ instead of $q\left(y|x\right)=N(x^2,1)$, since $y=x^2+\epsilon$ where $\epsilon \sim N(0,{0.15}^2)$. If the standard deviation of the noise is 0.15, then also the log-likelihood function in Footnote 3 should be adjusted.