1) You dont get smarter. Its not like knowing you are 120 vs 100 IQ changes anything about your ability to solve a problem
2) IQ is more of a speed of learning not an ability to understand. With enough time you can learn anything (challenge placed) the biggest barrier is discipline and desire.
3) IQ is abstract and is very useless within any context. If you want to know if someone is good at math give them a math test. If they are a good writer look at their portfolio. IQ is like determining someone is good at being a chef by only asking them questions. IQ is very far from any specific field of knowledge.
IQ is like space knowledge. Its only important/useful subject for a select few people.