He touched Frieda the wrong way
Horrid Henry's parents are called Mr. and Mrs. Henry.
The sentence "Mrs. Brown played the piano and Mr. Henry played the drums" is a compound sentence. It consists of two independent clauses ("Mrs. Brown played the piano" and "Mr. Henry played the drums") joined by the coordinating conjunction "and." Each clause can stand alone as a complete sentence, making it a compound structure.
Mr and Mrs
Mr and Mrs is correct or Mrs and Mr is correct
No -_-
Mr. and Mrs. (ex. "Hello, Mr. and Mrs. Evans" instead of "Hello, Mrs. and Mr. Evans")
Mr. & Mrs. Smith
It is a declarative sentence.
In the US it is normally Mr. and Mrs.
Dr. and Mrs. or Mr. and Dr.
I would address it to Mr and Mrs David Keys. For the salutation I would use Dear Mr and Mrs Keys.
Mr. used to be acceptable to address a household by just using the last name, e.g. "Mr. Jones". In modern times, it is typically to use "Mr. and Mrs. Jones" or "Mr. and Mrs. Timothy Jones".