Just open an account with ameritrade and test. Execution inside bid ask for otc markets are not instantaneous and sometimes take more than 10 minutes.
Your reply is a typical tactic used by con men, telling the other person to take action. You still offer no proof. Offer documented proof. That is the bottom line.
Which low commission brokers have any kind of "hidden", "invisible", "dark" or "iceberg" orders on their Android apps, other than Interactive Brokers? The latter say their new app "GlobalTrader" has no fee for OTC, but the info seems to be of doubtful quality. Normally, they are crazy expensive on per-share commissions.