When previously i made a some shape as " ***Make unique", after sometime if i forget which was that , how could i know that which was unique.?
Look at the component’s Definition name. It should have a number appended to it.
You can right-click on the new component in the Components panel, and choose Select Instances.
You can use the ‘Outliner’.
Or when in editing context of that particular component, check ‘Hide rest of model’ but uncheck ‘Hide similar components’. ( both of which can be assigned to their own shortcut keys to speed things up ! )
There is no technical difference between a component that was cloned with a single instance via “make unique” and any other component that happens to have only a single instance. As a result, almost all of the ideas given in earlier posts are not valid because they can’t distinguish between these two situations.
As @DaveR noted, since component definition names must be unique SketchUp uses the convention of appending “#n” to a name to assure uniqueness (where “n” is the smallest number that produces a unique name). However, it also does this when a user creates a new component and does not manually assign a definition name in the create component dialog. There is no way to tell whether “Component#4” was created by applying “make unique” to “Component#3” vs by creating a new component without manually assigning a name. Furthermore, there is nothing except required uniqueness that prevents a user from editing a definition name either to remove or add “#n” to the name. So even the test Dave proposed is reliable only if a user has the good discipline to always assign sensible definition names to all component definitions.
Perhaps my error to think that users should have good discipline…
Of course I know that many don’t.