Is it possible my magento 2.1.6 to magento 2.1.0 because my magento theme only support max version magento 2.1.0 that's why my theme products and some pages css and js not working and also every time run the deploy command it shows 12 errors. Any one let me help I tried that magento 2.1.6 to 2.1.0 it is shows some errors.
I'd rather fix the theme. I don't think Magento supports downgrading currently. You can try to change the composer required version and then run composer update. Maybe it works? I wouldn't bet on it though.
composer require magento/product-enterprise-edition 2.1.0 --no-update