Development Store Set Up But New Url For Products Not Working

Have set up a development, but the url for products and categories not updated to new url

I have placed the following into htaccess : RewriteBase /https://mystore/dev/

also tried rewritebase/mystore/dev/

I have updated the config local

I have cleared the cache both in the new dev store and in the administration panel

Categories are linking through to the main store front https://mystore/

Products are returning a 404 error Not found https://mystore/dev/productname

All help gratefully accepted

Kind Regards