import re
s = """vasya:true12
gena:false9999
petya:true888
oleg:falsetrue
fan:falsetrue909
qqq:01234567890"""
print(re.sub(r"^.*:(.{0,7}|((?!.*(?!\d)\w)|(?!.*\d)).*)\r?$\n?", "", s, flags=re.M))
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