Subject-Verb Agreement Error and Double Superlative?

Shown below is my self-explanatory email correspondence with The Editor of The Star's Mind Our English:-

To The Editor (on July 6)

I refer to the STAR METRO NORTH of July 6, the front page of which is showing the sentence under the headline Sparkling clean:The efforts of Ipoh's SM St Michael students and staff in maintaining their washroom in tiptop condition has not gone unnoticed by the authorities in Perak.

The sentence should have been "The efforts of Ipoh's SM St Michael students and staff in maintaining their washroom in tiptop condition have (and not has) not gone unnoticed by the authorities in Perak. (In essence the message is: The efforts have not gone unnoticed.)

Also in the news proper on page M3, the sentence (below the third/last picture/photograph) reading, "The washroom at SM St. Michael has been declared by the authorities as being the most cleanest among schools in Perak" should have been "The washroom at SM St. Michael has been declared by the authorities as being the cleanest among schools in Perak" since cleanest is already in the superlative degree - most is unnecessary. Regards, Kengt, Penang

The Editor's Reply (on July 9)

Thank you for pointing out the errors. I have sent the message to everyone in the Editorial Dept including the Group Chief Editor.

Best wishes,
Kee Thuan Chye
Associate Editor
Editor of Mind our English
The Star