The contrast in this sentence is between matters internal and external to the state.  The word “domestic” is derived from Latin roots for “home” found in words like “domicile” and “domesticate.”  The word has an extended meaning when applied to political affairs, indicating that certain classes of actions and undertakings are related to matters “at home” as opposed to those that are “abroad.”

Someone with “plenipotentiary” authority is authorized to act on behalf of a nation (or any other person / group / etc) in any fashion whatsoever.  Such a person is said to have “full authority,” a meaning that comes out in the literal meanings of the parts of the word.  “Pleni-” is derived from the Latin “plenus” meaning “full” or “complete” and is found in English words like “plenty” and “plenitude.”  The second half (“-potentiary”) comes from roots meaning “power” or “ability” and is related to words like “potency,” “impotent,” and “potential.”

Cognate words are ones that share the same lineage, such as the word “fenestra” in English (meaning “an opening in bandage or an opening made in the midst of a surgery”) and the French “fenêtre” (meaning “window”) are both derived from the Latin “fenestra,” (meaning opening for light or a window).  The word “cognate” literally means “of the same birth” or “with+born.”  The “co[g]-” prefix means “with” (like “cohabitate” or “coordinate”).  The “-[g]nate-” portion is derived from Latin roots related to birth.  Similar English words are “nativity,” “natal,” and “nascent.”

The key word to note is “arboreal” which indicates that the scenery in the hometown has something of a “tree-like” character (or, more likely, is filled with many trees).  Nothing is said about the seclusion of the area, and “pastoral” above all implies fields.  The word “sylvan” comes from the Latin “silva” for forest. 

The clues in this sentence indicate that George was a “preachy” type of person.  Such a person could be called “predicatory,” a rather uncommon word, but one with roots that you can perhaps see.  It really is a combination of “pre” and “dicactory.”  The prefix here means “before” in the sense of being “before (=in front of) the crowd.”  The later is related to words like “diction,” “contradict,” and “dictionary.”  Together the word makes an adjective describing one who speaks in front of a crowd.  

The implied contrast in this sentence is not merely a matter of expecting one personality type and unexpectedly finding another.  Although that is certainly true, the boy’s mother is shocked at the character of the criminal activities.  In contrast with an innocent and upright childhood, these activities would not only be unexpected but also “nefarious,” meaning “wicked” or “criminal.”

The key to this sentence is to strike a balance between strict equivalence and opposition.   An equivalence would not provide the needed distinction, and there is nothing in the sentence to indicate a complete contrast.  The word “cognate” strikes just such a balance.  Although it usually describes words that are descended from the same linguistic roots, “cognate” can also mean “related” or “connected.” The word literally means “of the same birth” or “with+born.”  The “co[g]-” prefix means “with” (like “cohabitate” or “coordinate”).  The “-[g]nate-” portion is derived from Latin roots related to birth.  Similar English words are “nativity,” “natal,” and “nascent.”

Clearly, the sentence wishes to express the depth of Rembert’s voice, but this does not imply anything about its loudness.  Do not be fooled by the word “imposing.”  It is the depth that is compared to his imposing appearance.  The word “sonorous” implies depth and fullness to a voice, which well matches what is needed here. 

Although it is difficult to tell if the sentence is looking for a contrast to the word “discordant” or a synonym to it, it should be clear that none of the options can be a synonym in any strict sense.  The metaphor of being “discordant” implies that something “clashes” with the moralist’s experience.  Therefore, if it must be a contrast, the word “consonant” would work best, as it implies that something is “in agreement with” his experience.  Literally, to be consonant means to “sounds with” something else.  Two agreeing notes in a piece of music are considered to be “consonant.”  The usage here is metaphorical. 

Although it might seem that a rigid schedule is difficult, we cannot imply that directly. The word “regimented” best fits the needs of this sentence, meaning “strictly organized in a strict schedule.”  The word is related to a number of words for “ruling” such as “regal,” “regent,” and “regalia.”