Which isomer among the following has the highest boiling point?

Identify substrate '$$\mathrm{A}$$' in the following conversion.

$$\mathrm{A}+\underset{\text { (excess) }}{\mathrm{CH}_3 \mathrm{I}} \stackrel{\Delta}{\longrightarrow} {\mathrm{C}_2 \mathrm{H}_5}\left(\mathrm{CH}_3\right)_3 \stackrel{+}{\mathrm{N}} \mathrm{I}^{-}$$

Identify the CORRECT decreasing order of basic strength of compounds from following.

Identify product $$\mathrm{B}$$ in the following reaction.