What are the minor Python version changes?

"Critical changes" depend on what you're paying attention to, so you might want to check the link below to find out what you need

• New features in Python 3.4 compared to 3.3: What's New In Python 3.4
• New features in Python 3.5 compared to 3.4: What's New In Python 3.5
• New features in Python 3.6 compared to 3.5: What's New In Python 3.6
• New features in Python 3.7 compared to 3.6: What's New In Python 3.7

It contains approximately the following items

• New Grammar Features:
• Change backward incompatible grammar:
• New Library Module:
• New built-in features:
• Improve CPython implementation:
• Significant improvements to standard libraries
• Improve security:

There is also a history of changes up to Python 3.7.10 final, so please refer to

• https://docs.python.org/ja/3.7/whatsnew/changelog.html