Yes, all trades must be held for a minimum of 180 seconds unless you purchase the Scalping Add-on at check-out. In that case, the minimum holding time is 30 seconds.
If this rule is violated, will held to a soft breach of the account. Any profit generated from those trades will be cancelled and any loss occurred will be calculated as per drawdown rules. If the rule is violated multiple times, it can lead to hard breach of the account.