Why my rank is changed from Jr Member to Newbie.
Because this forum comes with something new and appreciable system called demerit system.In this system 1 merit is necessary to become a Jr Member and 30 activity too.This step is OK for the Jr member and makes some trouble for newbies or brand new. But the next step after that was taken by the forum Moderator is to derank those user who have zero merits but they are still Jr Member their activity count does not help them to maintain their rank as Jr Member.
Should I do rank increasing by posting 2 posts per week to get again Jr Member ??
Onward now the numbers of your post either it is two or ten will not help you to rank up unless you make some efforts in writing a quality post.