Answered the 1st 4 sub-parts of the question as per Chegg's answering guidelines. This will provide with almost everything required for the next 2 sub-parts. Hope this helps!

All the explanations is in the code comments.

Code:

#include <iostream>
#include <fstream>
#include <stdlib.h>
#include<time.h>
#include <iomanip> // std::setprecision

using namespace std;

// (0) function does not take any parameters
// returns an integer representing your user's menu choice
int displayMenu()
{
int choice;

while(true)
{
cout << "Menu ----------------------- " << endl;
cout << "Choose 0 to exit" << endl;
cout << "Choose a function from 1 to 5" << endl;
cin >> choice;

// return valid user input
if(choice>=0 && choice<=5)
return choice;
}
}

// (1) function
void function1()
{
// required variables
string filename;
int rows, cols;
long double val;

// prompt the user for the name of a file to output as a text file
// that will hold a two dimensional array of the long double data type.
cout << "Enter name of output file: ";
cin >> filename;

// open file
ofstream fout;
fout.open (filename);

fout << "UNSORTED" << endl; // 1st line in file

// prompt the user to enter the number of rows
// and the number of columns for the two dimensional array.
cout << "Enter number of rows: ";
cin >> rows;
cout << "Enter number of columns: ";
cin >> cols;

fout << rows << " " << cols << endl; // 2nd line

// prompt the user to enter the values for each row
// and column element in the two dimensional array.
for(int i=0; i<rows; i++)
{
for(int j=0; j<cols; j++)
{
cout << "Enter value for (" << (i+1) << ", " << (j+1) << ") cell: ";
cin >> val;
fout << std::setprecision(15) << val << " "; // write value to file
}
fout << endl;
}

// close file
fout.close();
}

// (2) function like function #1, except this time,
// instead of asking the user for the values for each row and column element,
// have the function create a randomly generated values for the number of rows and columns
// (a minimum of 2 rows and 2 columns, and a maximum of 10 rows and 10 columns).
void function2()
{
// required variables
string filename;
int rows, cols;
long double val;

// prompt the user for the name of a file to output as a text file
// that will hold a two dimensional array of the long double data type.
cout << "Enter name of output file: ";
cin >> filename;

// open file
ofstream fout;
fout.open (filename);

fout << "UNSORTED" << endl; // 1st line in file

// Use current time as seed for random generator
srand(time(0));
// generate the number of rows and the number of columns
// for the two dimensional array. (between 2 and 10)
rows = rand() % 9 + 2;
cols = rand() % 9 + 2;

fout << rows << " " << cols << endl; // 2nd line

// prompt the user to enter the values for each row and column element in the two dimensional array.
for(int i=0; i<rows; i++)
{
for(int j=0; j<cols; j++)
{
long double a = (double)rand() / (double)(RAND_MAX);
long double b = (double)rand() / (double)(RAND_MAX);

// divide the smaller number by larger number
if(a<b)
val = a/b;
else
val = b/a;
// fprintf(fout, "%.15Lf\n", val);
fout << std::setprecision(15) << val << " "; // write value to file
}
fout << endl;
}

// close file
fout.close();
}

// (3) function
void function3()
{
// required variables
string filename, temp;
int rows, cols;
long double val;

// prompt the user for the name of a file to input as a text file
// to read in the two dimensional array of long double type.
cout << "Enter name of input file: ";
cin >> filename;

// open file
ifstream fin(filename);
if (fin.is_open())
{
fin >> temp;

// read rows and columns number
fin >> rows >> cols;

// read values
for(int i=0; i<rows; i++)
{
for(int j=0; j<cols; j++)
{
fin >> val;
cout << std::setprecision(15) << val << " "; // print contents
}
cout << endl;
}

// close file
fin.close();
}
else cout << "Unable to open file";
}

// main function
int main()
{
// sample run
while(true)
{
// user's choice for menu
int choice = displayMenu();

if(choice == 0)
{
break;
}
else if(choice == 1)
{
function1();
}
else if(choice == 2)
{
function2();
}
else if(choice == 3)
{
function3();
}
}

return 0;
}