Muchísimos gracias Carlos y Dionan!

I understand it. But it doesn´t sound natural to me. I would say "She is my only relative" or "She is the only relative that I have" If I wanted to stress the fact that she is alive, I would say: "She is the only relative of mine that is alive today"

yes!

I have breakfast. You have breakfast. He/She/ it has breakfast. you have breakfast. We have breakfast. They have breakfast. Notice that "has" is only used with "He", "she" and "it".

No they are not the same. "May not" indicates assumption. This means that there is a possibility that another opportunity happens again or there is a possibility that it does not happen again. We simple believe that the possibility of the opportunity happening again is less likely to happen than the possibility of the opportunity not happening again. "Won´t" means "will not". Therefore, another chance is absolutely not going to accrue.

I disagree with Cici I understand them perfectly. However, "for as long as" and "as long as" have the same meaning. However, your confusion here is the use of the world "for". When should you use it and when you shouldn´t use it? Unfortunately prepositions in every language are hard and there are sometimes no rules. For example: We say "in school" but not "in home". Using the Phrase "as long as" or "for as long as" will require seeing a lot of examples. Sometimes they are interchangeable like the sentences you gave. Sometimes only one can work. For example: She had loved me for as long as I can remember She had loved me as long as I can remember. (Without using "for" his just sounds wrong.) This answer is as long as can be. This answer is for as long as can be. (Using "for" just sounds wrong here.)

"A lot" is functioning both as an Adjective and as an Adverb in the sentence. Chocolate Cake does a lot. Here " a lot" is modifying the the verb "does" and by definition, a word that modifies a verb is an adverb. A lot of people. Here "a lot" is modifying the noun "people". By definition a word that modifies a noun is an Adjective.