Why should that be the best advice? If everyone just doing a border run we will never find out what requirements/ documents we need for the extension process. So why not find out at immigration when itโs time to extend
What Visa type did you actually apply for? There is no 90-Day tourist visa. The tourist visa is only for 60 days (valid for 3 months). Maybe you applied to wrong visa like the the 90-Day Non-Immigrant Visa?