How to simply insert month and year in middle of the paragraph?

You could simply define a macro which stores the relevant data, for example, you could use newcommandquestionDay{Monday} to store the day on which you asked this question. Then you could use questionDay in your paragraph wherever you want to refer to this day. However, keep in mind that spaces are ignored after macro names, so if you want a space following questionDay you could use questionDay{} instead.

Another approach could be to store the data in some data structure and retrieve that. The following implements such a data structure that you can initialize giving a macro name and a list of key=value pairs which store properties for this macro name. When you then use the macro it'll accept one argument, being one of the properties stored earlier, and it'll typeset that property's value.

This example shows both methods:

documentclass[]{article}

% basic approach
newcommandquestionday{9th}
newcommandquestionDay{Monday}
newcommandquestionyear{2020}
newcommandquestionmonth{November}

usepackage{xparse}

% property list based approach
ExplSyntaxOn
msg_new:nnn { Bhargav } { already-defined }
  { #1 ~ `#2' ~ is ~ already ~ defined. }
msg_new:nnn { Bhargav } { unknown~property }
  { The ~ property ~ `#2' ~ isn't ~ found ~ for ~ `#1'. }
tl_new:N l_Bhargav_tmp_tl
NewDocumentCommand newevent { m m }
  {
    prop_if_exist:cTF { c_Bhargav_event_ token_to_str:N #1 _prop }
      {
        msg_error:nnxx { Bhargav } { already-defined }
          { The ~ property ~ list ~ for } { token_to_str:N #1 }
      }
      {
        NewDocumentCommand #1 { m }
          {
            group_begin:
              prop_get:cnN
                { c_Bhargav_event_ token_to_str:N #1 _prop }
                { ##1 }
                l_Bhargav_tmp_tl
              quark_if_no_value:NTF l_Bhargav_tmp_tl
                {
                  msg_error:nnxx { Bhargav } { unknown~property }
                    { token_to_str:N #1 } { exp_not:n {##1} }
                }
                { l_Bhargav_tmp_tl }
            group_end:
          }
        prop_const_from_keyval:cn
          { c_Bhargav_event_ token_to_str:N #1 _prop }
          {#2}
      }
  }
ExplSyntaxOff

% defining a new property list
neweventdeathfreddie
  {%
    year=1991,
    month=11,
    day=24,
    Month=November,
  }

begin{document}
Bhargav Rajyaguru asked a question on questionDay{} the questionday{} of
questionmonth, questionyear.

It was very sad that Freddie Mercury died on
deathfreddie{year}-deathfreddie{month}-deathfreddie{day}. That was the
saddest deathfreddie{Month} in deathfreddie{year}.
end{document}