What is the differences between stereotype properties and tagged value in UML? I read about them but I don't know the main differences.
UML2.x has no tagged values. They are still defined in MOF but are removed for UML. Stereotypes have standard Properties. And those Properties are displayed as Properties of the extended Element (not with curly braces). They can be displayed using French quotes but can be any other way.
Stereotypes are a mighty concept to extend any Metaclass with additional Properties, Constraints and Dependencies. They are not comparable to the tagged values other than they are a extension mechanism as well.
A hands-on eclipse tutorial for UML2 stereotypes can be found here. You can scan through it to get an impression on the complexity.