You should backup your site before downgrading Woo-commerce plugin.

Follow steps below to dowgrade Woo-commerce plugin:

– Deactivate Woo-commerce plugin (don’t delete the Woo-Commerce plugin in the administration panel)
– Download Woo-commerce version that you want to downgrade (download link)
– Login to your hosting through FTP or Hosting Panel
– Browse to wp-content/plugins
– You will see Woo-commerce directory
– Replace the existing Woo-commerce directory with that newly extracted
– Activate Woo-commerce plugin