import re
 
regex = r"(?<=Version\s)\d+\.\d+(?:\([^()+]\)[A-Z]\d|\.\d{2}[a-z])"
 
test_str = ("String 1-Cisco IOS Software, C3900 Software (C3900-UNIVERSALK9-M), Version 15.4(3)M3, RELEASE SOFTWARE (fc2)\n"
	"ROM: System Bootstrap, Version 15.0(1r)M16, RELEASE SOFTWARE (fc1)\n\n"
	"String2-Cisco IOS XE Software, Version 16.05.01b\n"
	"Cisco IOS Software [Everest], ISR Software (X86_64_LINUX_IOSD-UNIVERSALK9-M), Version 16.5.1b, RELEASE SOFTWARE (fc1)\n"
	"licensed under the GNU General Public License (\"GPL\") Version 2.0.  The\n"
	"software code licensed under GPL Version 2.0 is free software that comes\n"
	"GPL code under the terms of GPL Version 2.0.  For more details, see the")
 
print (re.findall(regex, test_str))

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