Hello everyone, nice to welcome you on our site, this page even has Level 4 answers. I enjoy it =D
Level 4 - NNGGOOI
The answer to this puzzle is:
Words: NOGGIN, GONION, GOGO, GOON, NOG, ONO, GIN
Bonus words:
NOGGIN, GONION, GOGO, GOON, NOG, ONO, GIN