No, he can’t. Biden isn’t emperor, and the DEA is an independent agency. Presidents don’t just get to tell the DEA what to do. You clearly don’t understand how our government works. What he can do is have the Dept. of Health and Human Services order a review of marijuana’s scheduling, which he has done.
This on paper is effectively true, however the DEA is in part under the scope of the executive branch. In practice the president has enough influence over the DEA to practically give the head of the DEA an “order”. Or at least suggest that if his instructions are not followed that the head of the DEA should be job searching.
In other words, the head of the DEA would not move forward with following the recommendations of the dept of health without the approval of the executive. In all likelihood he could reschedule at any time, and I imagine that time will be based on the elections.