I have created my assembly and now I need to drag one sub-assembly, in order to represent a rotational motion of a hinge. I don't want to model the hinge. I just want to see if interferences exist in the asm.
To drag or rotate a subassembly you need to assemble it using connections. In case of a pin connection you can rotate it about the pin axis. In case if planar or cylinder you can drag it. To check the interference you use global interference under the command model analysis under the analysis menu.
Also if your mechanism is complete and you run it, then you can check global interference or between two parts, under the playback icon.
You can simulate a pin connection without having Mechanism (MDX). It sounds like you want two constraints: aligning axes (or inserting cylinders) and some kind of translational constraint (e.g., aligning datum planes). This should leave a rotational DOF unconstrained (about the axis).
Then, with the Component Placement dialog box still open (either when you're constraining or redefining the component), hold down <Ctrl> and <Alt> and use your mouse buttons. This is called freeform component packaging. In other words, manipulating the component (translate, spin, etc.) on screen instead of the whole model.