Remove the tank cover and check the water level after the fill valve has shut off. It should be about one inch below the opening of the overflow tube. If it is significantly lower than that, there may not be enough water in the tank to fill the bowl after a flush. Correct this by adjusting the float.
The average child can do this during the second half of this year. Between 24-36 months, children are typically able to work simple insert puzzles (e.g., completes a three-piece simple puzzle where pieces are whole objects). Also, children can remove a part from a toy (e.g., a wheel) and replace it.
As a newborn, your baby has an innate ability to grasp objects, but it will take him at least a year to develop the coordination to pick up and hold things securely in his hands. He'll start working intensively on this skill by 3 months and make leaps with each passing month.