Recently, my router is not stable, so I use my negibor's unsecured network to play NFS world. Is that illegal? will I get into trouble?
Yep, quite illegal.
The odds of you getting caught after about 3 months I would say about 60% chance.
Legit happened to my neighbors, one of them was a lesbian, and used another houses wifi to watch porn.
yes this is illegal.
high odds of getting caught!