Is the following sentence linguistically acceptable?
The hardest that it is believed that it has ever snowed here was last January 12th.

acceptable

Is the following sentence linguistically acceptable?
John is very fond of Mary.

acceptable

Is the following sentence linguistically acceptable?
Who had Poseidon run away, before the executioner murdered?

unacceptable

Is the following sentence linguistically acceptable?
Mr Knightley suggested that thieves would break into Hartfield.
acceptable