Hi Arti, As the UK is a collective name for a group of countries we use the article. The same is true for groups of islands or mountains For single countries or city names we don't use the article. For example 'I'm going to the UK' 'I'm going to the USA' 'I'm going to the Canary Islands' BUT 'I'm going to England' 'I'm going to London'

In English, we use the definite article “the” before the names of countries that are plural or have a common noun in their name. For example, we say “the United States,” “the Netherlands,” “the Philippines,” and “the United Kingdom.” Therefore, the correct sentence is “I’m going to go to the UK.”

Yes, you do. Honestly, as a practical matter, in my opinion the best "rule" is to copy usage from a reliable source. Wikipedia is good, and you can usually find a Wikipedia article just by including "wikipedia" in the search string. "wikipedia united kingdom" find an article which begins: "The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Northwestern Europe."

"I'm going to go to the UK"

yup, you need to use the in The UK