whats the difference? and application? whats the highest degree and levels of each? how many levels?

ב"ה Shalom, In order to answer this question, I must make a few clarifications at the onset. Firstly, all of these concepts must be studied in depth and you cannot suffice with what I'll write here, which is written in a concise form and barely touches the surface of the depth of these concepts. Secondly, in regard to the concept of Hitbodedut there are differences of perspectives in the definition by Breslav Chassidim and the concept of Hitbodedut as found in the Messilat Yesharim and others. According to the Messilat Yesharim (Intro. And chapter 3, and other Sefarim) the concept of Hitbodedut is primarily one of introspection. In other words, a person does a self-examination of where he stands in his relationship to Hashem, to his study of Torah and fulfillment of mitzvoth. Prior to the this, a person must put himself in a frame of mind without disturbances so he can actually contemplate about himself and do a process of self-criticism. It doesn't necessarily mean seclusion, but it requires to think without interference. In Likutei Moharan chapter 52, the concept of Hitbodedut according To Breslav , requires a particular secluded place, a time late at night and it speaks of talking to G-d directly. The purpose of the Hitbodedut is to bring about "Bitul", which means a form of self-nullification. In regard to meditation, since you are not referring to a meditation which brings about physical relaxation, but to a meditation about spiritual things, it's just another word to describe contemplation as I explained above from the Messilat Yesharim. Or perhapswe can explain it as described in Masechet Brachot 5a as explained by Sefer Charedim (Chap. 65) , that the early especially pious men , would wait an hour before prayer in order to focus their hearts to Hashem. This would be a serious concentration and focusing of their mental and emotional faculties to their prayer. As far as prayer, prayer, beyond the requests from Hashem, is seen by many commentators, (R. Yosef Albo in Sefer Ikkarim, Ramchal in Derech Hashem ) as an action of bringing the person to higher spiritual level by aspiring to the lofty concepts which are mentioned in the Tefilla making the person worthy to receive from Hashem's abundance. So all the things you mentioned are important spiritual concepts which a part of Jewish daily life, each thing applied in its proper time and dosage according to the individual spiritual growth of the person with most people doing Hitbodedut they were taught and with Breslav followers doing Hitbodedut as they were taught. All the best