Question 1)
grep --color '\.ipv[46]\.'  DIR/sysctl.conf
Question 2)
grep '^[^#]' DIR/sysctl.conf 
grep -v '^[#]'
Question 3)
grep -i '_root_' DIR/ca-certificates.conf
Question 4)
grep '_Class_[[:digit:]]' DIR/ca-certificates.conf
Question 5)
grep -l 'KEYMAP' -r 
Question 6)
grep --color -i '([[:lower:]]*)' Xorg.0.log 
Question 7)
grep '\.[[:lower:]]*\.[[:lower:]]' krb5.conf  -i --color
Question 8)
grep '[[:digit:]]*\.[[:digit:]]*\.[[:digit:]]*\.[[:digit:]]*' syslog --color
Question 9)