No, the Plant Pro-Tec Dog and Cat Repellent is not labeled for squirrels. This product will only repel cats and dogs.
The ?Plant Pro-Tec Dog and Cat Repellent (PP-RDC12) uses a special combination of natural ingredients such as garlic oil, lemon-grass, citronella, and cinnamon which are proven to repel dogs and cats effectively. The repelling odor would last 6 - 8 months. This being a natural product it will not harm the dogs, it will cast an unpleasant odor out so that the dogs will not wish to stay in that area.
According to the manufacturer of the Plant Pro-Tec Dog and Cat Repellent, people can smell the odor that it emits, but it is not strong or offensive.
Yes, Plant Pro-Tec Dog and Cat Repellent can be used on indoor plants, It is made of all natural oil ingredients, and would need be attached to the plant somehow like at the pot but it would not damage the plants in any way. Just keep in mind that this product intentionally has odor that may be objectionable for you to use indoors.