Why does Nepal have a history of frequent change of constitution? mention in a paragraph.

Because at the time of it's independence from Rana dynasty, a treaty was signed between Congress ,Rana's and the King. And an interim Constitution was formed in 1950 that charged Nepal into democratic country. And also during Rana dynasty The Rana's announced a constitution allowing some rights to citizen just to protect their rule. But this constitution never came into effect .

this is not a question its simply asking you to read and write a few sentences and   the question on the bottom its fairly easy, you can do this!

less available tax revenue

this basically means that when they get money from taxes wirth having a lower gdp they get less then what others have with a higher gdp