On your own
The checklist below names where to end up, not which keys to press. Use whatever you learned in this lesson.
Start with two jumps: one to line 20, one to the last line of the file. Both add an entry to the jumplist. Then retrace them without typing a line number or a search: walk back through the jumplist to line 20, and back again to line 1, where you started.
Watch the line number at the right end of the statusline; each step ticks when the cursor arrives.