Mention 3.1.1+ APIs in new optimization tutorials

tutorials/optimization/using_multimesh.rst

@@ -44,6 +44,9 @@ controlled with the :ref:`MultiMesh.visible_instance_count <class_MultiMesh_prop
 property. The typical workflow is to allocate the maximum amount of instances that will be used,
 then change the amount visible depending on how many are currently needed.
 
+.. note:: The :ref:`MultiMesh.visible_instance_count <class_MultiMesh_property_visible_instance_count>`
+          property was first added in Godot 3.1.1-stable.
+
 Multimesh example
 -----------------
 
@@ -65,6 +68,7 @@ efficient for millions of objects, but for a few thousands, GDScript should be f
         # Then resize (otherwise, changing the format is not allowed).
         multimesh.instance_count = 10000
         # Maybe not all of them should be visible at first.
+        # Note: Property only available in Godot 3.1.1 or later.
         multimesh.visible_instance_count = 1000
         # Set the transform of the instances.
         for i in multimesh.visible_instance_count:

tutorials/optimization/using_servers.rst

@@ -75,6 +75,10 @@ For nodes, there are many functions available:
   *instance base* via the :ref:`VisualInstance.get_instance() <class_VisualInstance_method_get_instance>`
   and :ref:`VisualInstance.get_base() <class_VisualInstance_method_get_base>` respectively.
 
+.. note:: The :ref:`VisualInstance.get_instance() <class_VisualInstance_method_get_instance>`
+          and :ref:`VisualInstance.get_base() <class_VisualInstance_method_get_base>` methods were first
+          exposed to the scripting API in Godot 3.1.1-stable.
+
 Just explore the nodes and resources you are familiar with and find the functions to obtain the server *RIDs*.
 
 It is not advised to control RIDs from objects that already have a node associated. Instead, server