When you solve this problem, in the academic background, thinking, logic and abstraction that consume your intelligence may be called mathematical thinking. No matter what your major is, learn math well, have a good foundation and be in an invincible position. Most doctoral supervisors like students with a good foundation in mathematics, especially those majoring in mathematics.
The second question I think is the speed of experience and industry change. I don't understand. The theoretical foundation established by actuaries may not be updated for a long time, but the IT industry is changing with each passing day, and the industry trends and technical directions are changing too fast. So IT engineers can't stick to the rules and need to keep learning. People can learn too much when they are old. I am a programmer majoring in mathematics, hehe.