It's mentioned in the constitution that no president can do any gov. job after his retirement, then how S. Rasdhakrishnan was teaching in Foreign or A. P. J. Abdul Kalam in Bihar.
The reason is the teaching is different type of service..
No, everyone is bound to abide by the rules of constitution, the reason behind this is other I will explain you later.
But in our country powerful people don't respect our constitution like sachin tendulker when it comes to tax paying, he mentioned himself as an actor otherwise we all know what he is, a player.when you are earning that much, what is the need for such things.still we love them,respect them.in case of kalam and radhakrishanan we can accept this type of things because they are legends and I respect them and it's nice to know this for me because in our country talented people don't work for government.and exceptions are rule of nature.