40 in the first team, about 30 in the reserves, which in total, is about 70 players!
3 I think
Manchester United have 32 players in their First Squad and two players are currently out on loan.
dimitar berbatov and some ovaz
6 players so far
Chelsea because they have fantastic players
Mark Hughes played for Man United, Chelsea and Barcelona. Bolo Zenden played for Chelsea, Barcelona and Liverpool
Mark Hughes has played for Manchester United and not Chelsea.
There are a few Michael Owen played for Liverpool , Manchester United and real Madrid. Nickolas Anelka played for Arsenal, Real Madrid and Chelsea. Diego Forlan has played for Manchester United and Villarreal and Athletico < Madrid.
Dennis Law and Carlos Tevez are players that formerly played for Manchester United and moved to Manchester City
Ricardo Carvalho and Paolo Ferreira ( Porto and Chelsea)
Mark Hughes and Veron
Manchester United is a better than Chelsea F.C. as Manchester United are ranked 3rd in Europe and Chelsea F.C. are 7th.
William Gallas - Chelsea and Arsenal. Ashley Cole - Arsenal and Chelsea. Mikael Silvestre - Manchester United and Arsenal. Emmanuel Petit - Chelsea and Arsenal. Nicolas Anelka - Arsenal, Liverpool (Loan) and Chelsea. Mark Bosnich - Manchester United and Chelsea. Andrew Cole - Arsenal and Manchester United. Mark Hughes - Manchester United and Chelsea. Jermaine Pennant - Arsenal and Liverpool. Paul Ince - Manchester United and Liverpool. Juan Sebastian Veron - Manchester United and Chelsea. Boudewijn Zenden - Chelsea and Liverpool. These are the few I know of for a fact. These are all since the formation of the Premier League.
Michael Owen (Manchester United and Liverpool) Ashley Cole (Chelsea and Arsenal) Nicholas Anelka (Chelsea and Arsenal) Michael Silvestre (Arsenal and Manchester United) ... I know that's not 12, but there are some for you!
The African footballers who played for Manchester United in the past are Clinton fortune.
No to my knowledge.