What should I do for those who have changed their rank on BTT to a newbie?
What should I do to become a Jr member like before?
Secondly you need to focus more on the quality of your post and work on your english if you are not verse in it already. Don't post one sentence responses in threads where there are thousands of pages and post. You want to actually bring some substance to your post that engages others, if you are going to post in mega threads atleast post something unique and relevant to the topic or current state of the coin/project.
Additional
Remember not only focus on the quality of posts, you also need to care about the environment, also contribute, if you find things that are suspicious, then help the forum to eradicate a variety of fraudulent actions, don't just keep quiet.
Many people will respect you, if you do one of the things that benefit others.
They will respect "you", but they won't give these guys merit.
Merit is a failed system, in terms of relying on other's to objectively give kudos to your words and thoughts.
You will not earn merit in any place dealing with alternative coins. The best place to earn is to go hug big donors in the BTT Meta section, that's the only place were there's a consistent output of merit from the vets of BTT.