Make a polyglot generator
Python 3, 167 bytes, produces Python 3.0, 3.1, ..., 3.9, 3.10, \${167 \over 11^2}\approx1.38\$
thanks to SuperStormer for refreshing my memory, allowing to add 3.10.

lambda r:'try:exec(&quot;%s&quot;);o=%d\nexcept:0\n'*10%sum(zip(&quot;0;int.bit_length;callable;u'';import enum;b''%();f'';breakpoint;(a:=0);{}|{}&quot;.split(';'),r),())+'print(o)'

Try it online!
This works by trying to evaluate expressions code that rely on new language features and updating the output value if successful. By including more subversions, the score could probably be decreased by quite a bit.




Version
Code
New Language feature




3.1
int.bit_length
New builtin


3.2
callable
New builtin


3.3
u''
Old syntax for unicode strings re-added from Python 2


3.4
import enum
New module called enum


3.5
b''%()
String formatting with % for bytes objects


3.6
f''
f-strings


3.7
breakpoint
New builtin function


3.8
(a:=0)
Assignment expressions


3.9
{}|{}
Dictionary union with |


3.10
a:x=0
postponed evaluation of annotations is now enabled by default