How to check if there is a plane during the signal routing ？

In the image, the shape is in the same layer as the routed signal, right? so, from the point of view of the tool, this is just a net that meets with a shape. I don't see how this can be separated from the situation where you ACTUALLY want to do that ... I know this is a mistake here, but how would you separate it from the corner case where you want to route a net into a shape?

I would use 2 SKILL features:

• Last click coordinate
• Point in shape

Run an impedance analysis on your DDR traces. If a DDR trace is referenced to a signal plane instead of a solid power/ground plane, its impedance will likely be incorrect and vary along its length, which SI tools will flag.
Simulate eye diagrams for your DDR signals. A "closed" or heavily degraded eye diagram can indicate serious signal integrity issues, including improper reference planes.
Advanced SI tools can visualize return current paths. If a DDR signal's return path is forced to jump over gaps or uses a non-ideal path due to a broken or block blast signal-laden plane, the SI tool will highlight this.