Question

Does Water boil at a temperature below
100°C in a pressure cooker?

Answer 1

because it is covered from all sides so heat does not go outside . and heat fastily

Answer 2

When we say that water boils at 100C, we mean that it boils at 100C at the atmospheric pressure of sea level, which is, for general purposes, 760 mm Hg (millimeters of Mercury), or 1 Atmosphere or about 1.01 bar . At higher elevations, such as Denver, CO, in the US, where the elevation is 1610 meters (5280 feet, or exactly one mile), the boiling point of water is 94.4C. Conversely, if you were to increase the pressure, the boiling point of water would increase. As near as I can find, typically, you'd have about 2 bar of pressure in a pressure cooker, which is about twice the pressure on the water at sea level, increasing the boiling point of water to 120C.
That's pretty much the whole point of a pressure cooker... to increase to possible temperature in the vessel to a point higher than is possible without it. This is why things like dry legumes (beans, lentils, peas, etc.) cook faster. That said, if you've never used a pressure cooker before, read the directions carefully, get somebody to show you how and watch some YouTube videos. Seriously, if you don't have it cooled down when you open it, bad things can happen (although, most modern pressure cookers have safety devices that prevent that from happening).