Underdeveloped
You can, when you're not using it in a derogative way.
Mucama is the right word, some people say "sirvienta/criada" but its a little derogative.
País emergente
Yes, in the case of referring to the countries characterized by what we call "Third World," then yes, as I understand. But in an arbitrary sentence talking about say, a third planet or something, like "it's almost the same as our world but there's a second and a third world" then no capitalization is needed. Excuse the horrible example.
In what five (5) ways can you say the trans-Atlantic slave trade contributed to the process of underdevelopment in the third world countries??
There really is no official list of the most popular sports but I would say hockey is not the third most popular sport in the world. Baseball, basketball, football , and soccer are all more popular but i would say hockey is close behind.
Some say that overpopulation and lack of access to clean water are the main causes of depeasantisation in third world countries. Government corruption could be another contributing factor.
non is no
We say lower third in spanish like this-el tercio inferior.
A third is "un tiers" in French.
that is non sense
Non-believers say that vampires don't exist.