You've identified the first dependent clause -- but it is not an adverb. It answers WHAT after the verb.
In the second sentence, the clause must include the verb and complements. Yes, it's a noun clause.
All family members know why the dog must leave.
Why the dog must leave? Adverb
They realize that the dog will become a visually challenged person's constant companion.
They realize that? Noun
In the second sentence, the clause must include the verb and complements. Yes, it's a noun clause.
The second is they realize that the dog will become?
You still don't have the complete dependent clause in the second sentence.
The second still confuses me because I have to leave an independent clause after naming the dependent clause....
Independent clause: They realize
Dependent clause: that the dog will become a visually challenged person's constant companion.
In fact, a visually challenged person can handle most traveling situations if a guide dog is with him or her.
If a guide dog is with him or her?
Adverb?