in The King ***
Yes
yes
No. It's not necessary.
No.
No.
Yes, T-shirt is correct.It is not necessary to capitalise the 't' in t-shirt. It is not a proper noun, but just a common noun. Capitalisation is not necessary even though the t-shirt was so named because it resembles a capital T.
You do, because they are proper nouns.
If a person is referring to the monarchy system of government, it isn't necessary to capitalise it. However, if the person is referring to the British Monarchy itself, then it is proper to capitalise it.
Greek Mythology or Greek Myth.
You can capitalise it if you want.
When you are referring to the planet Earth.At the beginning of a sentence.
No, there is no need to capitalise fitness in a sentence.