• open
  • vim -p
  • :tab split
• close
  • tabclose
• next
  • normal mode: gt
  • :tabn
• prev
  • normal mode: gT
  • :tabp

• dgg delete to beginning of file
• dG delete to end of file

To do this, move to the a in the first line, then press Ctrl-V (or Ctrl-Q if you use Ctrl-V for paste), then jj to select a visual block over three lines.

Now type I to start a special form of insert mode, then type the wanted text (s:). When you press Esc to exit from insert mode, the text will be inserted in the same position on each of the lines affected by the visual block selection.