Question

1. Did Mr. Fleming save Sir Winston Churchill when he was in a swamp/bog?
(is this story real?)

2. What saved Winston Churchill?
- It's penicillin.
- It was penicillin.
(Which answer is grammatical?)

3. Sir Winston Churchill
3-2. Sir Winston
3-3. Sir Churchill
(Which one is not correct? Why is so?)

4. He graduated from a medical school of Harvard University.

4-2. He graduated from a medical school in/at Harvard University.

(Which preposition do we have to use?)

Answer 1

1. I think it's not true!
http://www.snopes.com/glurge/fleming.asp
Your sentence is fine. Use the word "bog."

2. past tense

3. Sir Winston Churchill <~~ best
Sir Winston <~~might be OK
Sir Churchill <~~I've never heard that.

4 and 4-2: He graduated from Harvard Medical School.