If you write emails with a mix of Chinese and English to your subordinates, it seems okay. If you do that to your boss, I don't think it's appropriate. :P

It means the same thing - if. But because I've done a lot of reading recently, I found that 倘若 is commonly used in legal documents of Hong Kong. We would say 假如 a lot, informally. In formal writing or documents, 假如 would be replaced by 若 or 如.

1, If you look at the definition of "purge" in Oxford online dictionary, there is only one meaning for "purge" as a noun, which is "an abrupt or violent removal of a group of people from an organization or place". In your first sentence, it clearly doesn't indicate a removal of people, but emotions. Now let's see the definition of purification - "the removal of contaminants from something" or purge - "rid (someone) of an unwanted feeling, memory, or condition, typically giving a sense of cathartic release". Both are applicable to the context of the first sentence. It might need some time to check dictionary for these definition, but usually it is useful for self-study. 2, Both historical/historic events/sites are okay, but they are slightly different. "Historic", defined as "famous or important in history, or potentially so", highlights the influence or importance of one in history, while "historical" is "of or concerning history; concerning past events", which means anything occurred or related to the past can be historical. The Battle of Waterloo is a historic event, for example, but other campaigns that Napoleon Bonaparte involved in are historical fights. 3, I'd recommend "appearance" (definition: an act of performing or participating in a public event) in your third sentence.

That means: the initial (first) term of the Agreement is 2 years, and if it is not terminated (= does not violate the Clause 22), it will be automatically extended for one more year.

Thank you!