The main light element produced in stars through nuclear fusion is actually hydrogen, which fuses to form helium in the cores of stars. Additionally, while boron is indeed present in some stellar processes, it is not a primary synthesis product like helium.
As for heavier elements, large stars can produce elements up to iron through the process of nucleosynthesis during their life cycles, particularly in their later stages before they explode as supernovae. Elements heavier than iron, such as cobalt, are primarily formed during supernova explosions through a process called neutron capture.
Therefore, the statements should be corrected as follows: The main light element produced in stars is hydrogen, and the heaviest element that can be produced during normal stellar processes in large stars is typically iron (not cobalt). Cobalt and other heavier elements are produced in supernova events.