Need help from my fellow friendly expats

(not the ones who sit by the computer bored with shaking hands as they wait for post in forums to write smart ass replies to)

For my helpful expats, I have two questions, one for myself, one for a friend.

1) my friends B visa expires in 2 weeks. Some are saying they can go to immigration to have it changed to a tourist visa, others are saying they must leave the country to change it, which is true?

2) I’m hearing from many that kids under, I believe 16 don’t need a visa here in Thailand, is this true or no?

Thank you in advance to my fellow expats that provide insights.