Can I use regular guitar strings on a 30 inch guitar?

No, you cannot use regular guitar strings on a 30 inch guitar. The scale length of a guitar is the distance from the nut to the bridge, and the tension of the strings is determined by the scale length. A 30 inch guitar has a shorter scale length than a standard guitar, so the tension of regular guitar strings would be too high for the guitar and could damage it. You need to use strings that are specifically designed for a 30 inch guitar.