Mr. Lamb, a character in the story "The Third Level" by Jack Finney, tells several things about himself. These include:

a) He had a tin leg:
Mr. Lamb reveals that he lost his leg in a train accident many years ago. As a result, he wears a prosthetic leg made of tin. He explains that it is not a comfortable or realistic replacement but is functional enough for him to walk with.

b) Still, he was happy:
Despite his physical disability, Mr. Lamb maintains a positive outlook on life. He states that he is happy and content with his situation. This suggests that he has accepted his condition and does not let it define his happiness.

c) He never minds even if children teased him:
Mr. Lamb mentions that children often tease him because of his tin leg. However, he states that he never minds it and even finds it amusing. This shows his resilience and ability to overlook the negative actions of others.

d) All these:
The correct answer to the question is option 'D'. This means that all of the statements mentioned above are true. Mr. Lamb shares all of these aspects about himself during his conversation with the narrator.

Overall, Mr. Lamb is portrayed as a character who has faced adversity but has managed to find happiness and contentment in his life. Despite his physical limitations and the teasing he receives, he remains positive and unaffected. His character serves as an inspiration and highlights the importance of resilience and a positive mindset.