How to clear css/js and LSCache with code?

LScache plugin is OpenSource, so everything you need can be found in source code.

https://github.com/litespeedtech/lscache_wp/blob/master/src/purge.cls.php

please check this page

https://docs.litespeedtech.com/lscache/lscwp/api/#purge

qtwrk, do you know the specific hook that I can use to clear the css/js cache?

actually I think there is none

you can simply delete the content inside of /wp-content/litespeed/css/ or /js/

but not recommended, if only remove js/css without purge page cache, you could lead to 404 error on js/css files.