Hyperconjugation, arising from the interaction between the C-H sigma bond electrons of an attached methyl group and the vacant p-orbital of a carbocation, provides stabilization. This electron density delocalization mitigates the carbocation's positive charge.
Consider the reaction given below:

\(\text{A gives positive Fehling's test. Choose the correct relation}\).
Write the correct order of rate of reaction of following compounds with $PhN_2Cl$
P: $N,N$-dimethylaniline
Q: $N,N$-dimethyl-3-methylaniline
R: $N,N$-dimethyl-2,6-dimethylaniline
Most preferred site for electrophilic substitution in above example?
(Note: The molecule contains a nitrogen-containing ring and a carbonyl-containing ring, labels are U, S, R, P).