Microwaving a small amount of water for a few seconds should only warm it up slightly, and it's unlikely to become super hot or dangerous. However, it's important to exercise caution when handling hot objects or liquids to avoid burns or accidents.
If you heat a small amount of water for just a few seconds, it might not reach boiling temperature, which is typically around 100 degrees Celsius (212 degrees Fahrenheit) at sea level. The exact temperature will depend on the wattage of your microwave and the initial temperature of the water.
When you add something cold like ice to warm water, the ice will start to melt and transfer its coldness to the surrounding water. This process is called heat transfer, and it occurs until both the ice and the water reach a common temperature. The final temperature will depend on the quantities of water and ice and their initial temperatures.
To be on the safe side, it's advisable to use caution when handling hot liquids or objects. If you're unsure about the temperature of the water, you can always test it with a thermometer or let it cool down for a short period before adding ice or placing your hand in it.