How to change font in the entire SVG file when editing in Inkscape?

Question

I have opened an SVG file in Inkscape after haven't changing it for 1-2 years (the file is stored in a git repository and now I have to perform some changes) and suddenly wrong font is used to render it -

While my font should be serif and in fact when I open the SVG file in text editor I see:

<text
     id="text3683"
     y="220.98315"
     x="7.3200684"
     style="font-style:normal;font-weight:normal;font-size:11px;font-family:Monospace;-inkscape-font-specification:Monospace;text-align:center;text-anchor:middle;fill:#ffffff;fill-opacity:1;stroke:none"
     xml:space="preserve">

when I open the SVG file in Inkscape 0.92.3, a sans serif font is being used:

So I make sure that the layer (called "Squares") is not locked and try to change the font, but this setting is not applied:

Below is my exported (1-2 years ago) PNG file, please help me to get "back in time", i.e. to change the font in the entire SVG document using Inkscape back to the font shown below:

Answer 1

Nevermind, I have found a solution for my problem -

Whenever I selected letters, they where grouped (and probably that is why the "Apply" button in "Text and Font" dialog was greyed out):

Only after I have selected in the Inkscape menu: Object -> Ungroup, I have been able to press CTRL-SHIFT-T and set the font ("Courier New", Bold, 11 in my case):