If you already installed composer and if you want to change the composer version the use below command.
composer self-update --1
When you want to go back to version 2 (which you should, after updating or removing the incompatible plugins):
composer self-update --2
The above will take you to the latest on any of the two major versions.
You can also “update” to a specific version just by passing the version number to self-update:
composer self-update 1.10.12 composer self-update 2.0.7