There is a keyboard shortcut to select the first column in a row, but as far as I know there is no shortcut for the first row in a column.
You can press the Home key to select the first column in the current row.
Selecting the first row in the current column is not so easy. Here are a couple of ways.
Hold Ctrl then press Space Bar then press the full stop . then press the Up arrow. You can release the Ctrl key after the full stop.
F5 function key
Press the F5 function key then type in the cell reference eg d1 and then press Enter. You can do this to select any cell in the sheet.