RE:Question...Pre opens at 6 am, usually most programs active at 7 am est. For post market, close is 8 PM est and I check at 7:30 est if I want to enter or exit although if concerned do this before close or in the 30 min following close.
Suggest you you look at Nasdaq post market trading to get familiar with big spread low to high post market.
Uvxy had a good run 2:00 to 3:15 on Friday but collapsed. Typical and not rising in post market.
Cheers Manx