Answer to Question 1
In this piping system the main supply pipe from the boiler enters the first baseboard unit. The outlet from the first unit is connected directly to the inlet of the second unit. This arrangement is continued until all baseboard sections are connected in series. The outlet from the last section is connected to the circulator pump, which connects to the boiler.
Answer to Question 2
Baseboard heaters, convectors, fan coil units, and radiators