Google-sheets – “the key” in the Google Sheets URL

Google Query Language will return a JSON string. To get the cell value and format as you see in the spreadsheet, instead of /gviz/tq?tq= and the query string, use /pubhtml?gid= and the "right" parameters.

The easiest way is to get the URL resulted of publishing the spreadsheet to the web. Then...

Add range=A1 to the URL of the published spreadsheet, where A1 is the cell that you want to display.

I.E. for https://docs.google.com/spreadsheets/d/1NIIqpRSYCXT0OlvDgXa0g4GVxmrnvQOSn_L-HcgPqVA/pubhtml?gid=0&single=true

to display only the cell B13, the resulting URL is:
https://docs.google.com/spreadsheets/d/1NIIqpRSYCXT0OlvDgXa0g4GVxmrnvQOSn_L-HcgPqVA/pubhtml?gid=0&single=true&range=B13

to remove the header, add chrome=false:

https://docs.google.com/spreadsheets/d/1NIIqpRSYCXT0OlvDgXa0g4GVxmrnvQOSn_L-HcgPqVA/pubhtml?gid=0&single=true&range=B13&chrome=false

Note:
Use ? before the first parameter.
Use & when adding the second and subsequent parameters.

References
Publish a document, spreadsheet, presentation, or drawing - Docs editors Help
Cómo publicar en Web un rango - Ejemplos para los foros (How to publish a range in the Web - Examples for forums, self citation)

The following are three distinct characters:

"   34
“   8220
”   8221

and although the help file for IMPORTRANGE mentions only ...either be enclosed in quotation marks or be a reference to a cell containing... the required quotation marks are the "straight" ones.

So just use ".