I know a guy that's found out about his child when she was 4, after the girl had many guys tested. They took 7000 dollars from him last year now the what more should he have to pay all back support or should it just go from the time he found out

It depends on the court order, when he was served for child support, when he went to court to defend and to ask for child visits, what did the judge say and what was the order to pay.

Normally he would not pay back past the time support was ordered, but the judge could, esp if he failed to even show up to defend hisself

Depends on where you live... some states require CS to be paid from the date of birth, others allow this to happen on the date of the filing of a claim by , a third part of the states are left to the discretion of the judge