Does Wavelet Packets (WPT) decompose signal on dyadic scales like DWT?
I suppose  you are talking about $2$-channel DWT. WPT may have  slightly different  interpretations. With DWT, one only allows to decompose frequencies "downward ", ie after lowpass and subsampling. WPT allows to further decompose, at each level, after (lowpass or highpass) and subsampling. In that sense, WPT are a generic scheme, of which the DWT denotes a specific branch. The decision to decompose or stop at each level is governed by rules "external" to wavelets: frequency target, entropy, etc.

Another vision is the uniform WPT, or full wavelet packet, where at each level, both outputs are further decomposed, generating a uniform frequency splitting. 

So basically, you are correct at question 1. For question 2, when a DWT subband is approximately located (in reduced frequencies) between two successive dyadic bounds $[2^{-j-1},2^{-j}]$, a WPT can be located between any two dyadic rational bounds $[k_1 2^{-j_1},k_2 2^{-j_2}]$, with $j, j_1,j_2$ nonnegative integers, $k_1 \le 2^{j_1}$ and $k_2 \le 2^{j_2}$. 

For instance, the upper DWT subband only (approximately) localizes stuff in $[1/2,1]$, while you can reach  $[5/8,3/4]$ with a WPT. However, the aliasing comes into play, and this $[5/8,3/4]$ is disturbed by aliased components from other frequencies.  Aliasing is considered more severe for high frequency wavelet packet coefficients.

With $M$-band DWT and WPT, both structures remains $M$-adic at each level, but the WPT tends to split the subband axis onto $M$-adic fractions, with form $k/M^j$.