Project dependencies and constraint

Community,

wondering whether IFS projects really has the restriction to the dependencies and constraint that you scheduled, or this is just for planning purpose, will not do any control on the activity behavior?

for example, activity 1 and activity 2, i set the dependency between these 2 activities is Finish to Start. Does the system really will stop me if I start working on activity 2 (Release, create order, purchase receipt and etc..) before closing the activity 1?

same question to constraint.  if the activity is set to Start Not Earlier Than….., does the system really will control user’s activity to the project activity not starting the activity until the date we assigned?

Thank you.