Hi Elsta,
1.
Size and place the table as you want it, then select the table and go Arrange > Lock.
Note that Lock also prevents the user from entering data or editing formulas on the table.
Lock does not, however, prevent existing formulas from recalculating, so if this is a table used primarily for printing, you might consider putting the data entry functions into a separate (unlocked) table, and using formulas to transfer that data to this one, allowing this one to remain locked at all times.
2.
Individual cells, rows or columns cannot be locked in Numbers. You can manually set the height of the row and/or the width of the column of one or more selected cells using the Table Inspector. Once set, these sizes will remain fixed, despite changes in the size of their content, until you reset them. If the row is moved (by dragging the Row reference tab to a new location), the row size setting will be maintained. If an individual cell is moved, it's the content, not the cell that is being relocated, and the row height/column width settings will not follow.
Regards,
Barry