When using .getRange() on a Spreadsheet class object, it only accepts A1 Notation. What you want to do is use .getRange(i, j) on a Sheet class object. Adding this line after setting the active sheet would fix this:

spreadsheet = spreadsheet.getActiveSheet();

However this can be further simplified. Here are two versions of the complete function. First, with different formats for each of your data types:

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function myBorder() {
var spreadsheet = SpreadsheetApp.getActiveSpreadsheet().getSheetByName('Sheet1');
for (i = 1; i < 20; i++) for (j = 1; j < 20; j++) {
var range = spreadsheet.getRange(i, j);
var val = range.getValue();
if (Object.prototype.toString.call(val) == "[object Date]") {
range.setBorder(true, true, true, true, null, null, "blue", SpreadsheetApp.BorderStyle.DOTTED).setBackground("mistyrose");
} else if (typeof val == 'number') {
range.setBorder(true, true, true, false, null, null, "green", SpreadsheetApp.BorderStyle.DASHED).setBackground("powderblue");
} else if (val == '공란') {
range.setBorder(true, true, true, false, null, null, "black", SpreadsheetApp.BorderStyle.SOLID).setBackground("#E2E2E2");
} else if (typeof val == 'string' && val.length > 0) {
range.setBorder(true, true, true, true, null, null, "black", SpreadsheetApp.BorderStyle.SOLID_MEDIUM);
}
}
}

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Second, with one format for all data types:

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function myBorder() {
var spreadsheet = SpreadsheetApp.getActiveSpreadsheet().getSheetByName('Sheet1');
for (i = 1; i < 20; i++) for (j = 1; j < 20; j++) {
var range = spreadsheet.getRange(i, j);
var val = range.getValue();
if (val == '공란') {
range.setBorder(true, true, true, false, null, null, "black", SpreadsheetApp.BorderStyle.SOLID).setBackground("#E2E2E2");
} else if (Object.prototype.toString.call(val) == "[object Date]" || typeof val == 'number' || typeof val == 'string' && val.length > 0) {
range.setBorder(true, true, true, true, null, null, "black", SpreadsheetApp.BorderStyle.SOLID_MEDIUM);
}
}
}

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To improve efficiency, we can build a RangeList array for each value type. To separate numbers from currencies without checking the cell formatting (too slow), we can test the display value against an array of currency characters.

There is also an added variable for looking for a specific date. Currently, this ignores the GMT timezone because Daylight Savings Time was being ignored on one end. Someone else might know better how to account for that.

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function myBorder() {
var spreadsheet = SpreadsheetApp.getActiveSpreadsheet().getSheetByName('Sheet1');
var specDate = new Date(2023, 2, 2);
var rows = 20;
var columns = 20;
var array = spreadsheet.getRange(1, 1, rows, columns).getValues();
var display = spreadsheet.getRange(1, 1, rows, columns).getDisplayValues();
var currencies = ["Lek", "؋", "\\$", "ƒ", "₼", "৳", "Br", "BZ\\$", "\\$b", "KM", "P", "лв", "R\\$", "៛", "¥", "₡", "kn", "₱", "Kč", "kr", "RD\\$", "£", "€", "¢", "Q", "L", "Ft", "₹", "Rp", "﷼", "₪", "J\\$", "₩", "₭", "ден", "RM", "₨", "₮", "د.إ", "MT", "C\\$", "₦", "B/\\.", "Gs", "S/\\.", "zł", "lei", "₽", "Дин.", "S", "R", "CHF", "NT\\$", "฿", "TT\\$", "₺", "₴", "\\$U", "Bs", "₫", "Z\\$"];
var spec = [];
var date = [];
var cur = [];
var num = [];
var blank = [];
var string = [];
for (i = 1; i < rows; i++)
for (j = 1; j < columns; j++) {
var val = array[i - 1][j - 1];
var disp = display[i - 1][j - 1];
var r1c1 = `R${i}C${j}`;
if (Object.prototype.toString.call(val) == "[object Date]") {
if (val.toString().split('GMT')[0] == specDate.toString().split('GMT')[0]) {
spec.push(r1c1);
} else date.push(r1c1);
} else if (typeof val == 'number') {
if (val != disp && currencies.some(e => new RegExp(e).test(disp))) {
cur.push(r1c1);
} else num.push(r1c1);
} else if (typeof val == 'string' && val.length > 0) {
if (val == '공란') {
blank.push(r1c1);
} else string.push(r1c1);
}
}
if (spec.length) spreadsheet.getRangeList(spec).setBorder(true, true, true, true, null, null, "blue", SpreadsheetApp.BorderStyle.SOLID_THICK).setBackground("mistyrose");
if (date.length) spreadsheet.getRangeList(date).setBorder(true, true, true, true, null, null, "blue", SpreadsheetApp.BorderStyle.DOTTED).setBackground("mistyrose");
if (num.length) spreadsheet.getRangeList(num).setBorder(true, true, true, false, null, null, "green", SpreadsheetApp.BorderStyle.DASHED).setBackground("powderblue");
if (cur.length) spreadsheet.getRangeList(cur).setBorder(true, true, true, false, null, null, "green", SpreadsheetApp.BorderStyle.DASHED).setBackground("cyan");
if (blank.length) spreadsheet.getRangeList(blank).setBorder(true, true, true, false, null, null, "black", SpreadsheetApp.BorderStyle.SOLID).setBackground("#E2E2E2");
if (string.length) spreadsheet.getRangeList(string).setBorder(true, true, true, true, null, null, "black", SpreadsheetApp.BorderStyle.SOLID_MEDIUM);
}

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