Will it cut?

Really. Everything happens in the page. Disconnect from the internet after this page loads and the tool still works, which is the easiest way to prove it to yourself.

STL files carry no units at all, which is the single most common cause of a model arriving 25 times too big or too small. This tool assumes millimetres. If the dimensions look about 25 times too small, your file is in inches, so use the scale slider at 2540%.

Reliefs are often exported lying on their side or upside down, usually because the modelling software and the CAM software disagree about which axis is up. We test all six directions, and if one of them has the flat back the model needs, we tell you which way to turn it. Every number on the page then assumes you have.

That means there is no flat face in any of the six directions, so no amount of rotating will let a router reach the whole shape from one side. Cut it as two halves and glue them, use a 4th axis, or 3D print it.

A hole in the mesh. A watertight model has every edge shared by exactly two triangles. A few open edges usually cut fine. Thousands mean the file is damaged and your software may refuse it or produce strange toolpaths.

As a rough order of magnitude, yes. It is deliberately simple and does not know about your ramping, your lead-ins or your tool changes. If it says four hours, expect somewhere between three and six.