The Articles could not afford this protection because they could not collect taxes. Why is that?

The Articles of Confederation did not allow federal collection of taxes because it was a right of the individual states. As they had just been under the ruling of a centralized government (Parliament in Great Britain), the Articles did not want to repeat this system of government as it was despised by the American people, so many powers (such as taxation) were divided amongst the states. I hope that helps!!

the imf provides economic advice and loans to developing countries.

economic advice:

policy advice to governments and central banks based on analysis of economic trends and cross-country experiences; research, statistics, forecasts, and analysis based on tracking of global, regional, and individual economies and markets; technical assistance and training to countries improve the management of their economies.

loans:

loans to countries overcome economic difficulties; concessional loans to fight poverty.

these are the goals the fund wants to achive.