Just use level select to complete level 20.
You can do that for all other achieves to complete those specific levels for 1000G. Here's video guide showing levels 1 through 20 with timestamp below.
Level 1 - 00:27
Level 2 - 00:50
Level 3 - 01:35
Level 4 - 02:18
Level 5 - 03:14
Level 6 - 04:30
Level 7 - 05:08
Level 8 - 05:54
Level 9 - 06:36
Level 10 - 07:40
Level 11 - 08:55
Level 12 - 10:15
Level 13 - 11:26
Level 14 - 12:08
Level 15 - 13:32
Level 16 - 14:10
Level 17 - 15:56
Level 18 - 17:12
Level 19 - 17:59
Level 20 - 19:30