Re: 'Klopp always plays weakened teams in the FA Cup'
This is the lineup he put out against Everton in the FA Cup 3rd round in January 2018:
Karius, Gomez, Matip, van Dijk, Robertson, Can, Milner, Mane, Lallana, Oxlade-Chamberlain, Firmino.
Subs: Wijnaldum, Lovren, Klavan, Ings, Solanke, Ward, Alexander-Arnold.
Salah, Henderson and, erm, Coutinho were injured, so it seems like the only first teamers rested were the 19-year-old Trent and Wijnaldum. Pretty strong team, and not a kid in sight. Of course, context matters etc, but food for thought.