You can make a trade eligible for execution during extended hours by turning on the toggle for it when placing an order. You always retain control of the toggle (which remains off by default) for each order you enter.
Not all securities may be available for trading during Extended Hours. The availability of a particular security may vary based on several factors, including the interest in that security during pre-market or after-hours sessions and as would be made ...
OTC securities are over-the-counter (OTC) securities that are traded through a network of broker-dealers (as opposed to a centralized exchange such as NYSE or NASDAQ). OTC stocks typically cover foreign companies, ADRs, and some smaller companies ...