Why do the IPs of some routing nodes change dynamically?

1.Why do the IPs of some routing nodes change dynamically? For example:
In 2022-10-24-00-00-00-consensus file, the IP of the node named EinfachOhneNamen is 91.40.121.88.

But in 2022-10-24-08-00-00-consensus file, the IP of the node named EinfachOhneNamen is 91.40.113.252. They belong to the same /16 network segment.

  1. Currently, many countries prohibit access to Tor, such as China. Do you have any good ways to use Tor to access websites in these countries?

Must be dynamic to avoid begin be traced back ?