I don't know anybody perfect in this world. The Buddha, he was the only perfect one that I know of, according to the scriptures.
"Cope with the difficulties?" That is not to get swept away by them. Sometimes we can feel overwhelmed by them, even when we have some techniques and tools. Coping with them means not going under and raising the courage to deal with them until we can understand them and let them go.
"Please explain the differences between methods, techniques and tools of mental development." Sometimes we say these different words because we are teaching people who are not English speakers. So it doesn't mean there is a difference between them, we just often give a different word, so that some people who don't have perfect English will be able to get one of them at least and know what we are talking about, but it doesn't mean there is a difference. No matter what word we use we are talking about the Buddha's teachings.