Q1. Yes, Click on the row number after your last row (i.e. 31) thus highlighting that row. Use CNTRL SHFT Down Arrow to select remaining rows. Right click and "Hide" The same can be done with columns using the Right Arrow.

Q2. You can use "Data Validation" but if the user pastes the value in rather than manually entering it, the data validation disappears. Let me know if you want that explained. For the VBA, you'll want to copy the below code into your workbook module and modify it for your data. 
Private Sub Workbook_BeforeSave(ByVal SaveAsUI As Boolean, Cancel As Boolean)
If Worksheets("Sheet1").Range("A1") = "" Then   
MsgBox "You must enter blah blah blah"
Cancel = True
End If
End Sub

Private Sub Workbook_BeforePrint(Cancel As Boolean)
If Worksheets("Sheet1").Range("A1") = "" Then   
MsgBox "You must enter blah blah blah"
Cancel = True
End If
End Sub
Change the worksheets name and the range to match your data.
To paste into workbook module
ALT + F11 to enter VBA Editor
You should see a folder like window on the left with your worksheets and a folder called "ThisWorkbook." Double click on "ThisWorkbook".
Paste the code into the white text window on the right. Close the VBA editor (no need to save, it will save with the workbook)
Did that help?