You claim that you are not the father of your child and you have DNA test report which substantiate your claim. IF this is 100% true, you will be eligible for divorce on grounds of cruelty. Since she is not your biological daughter, you will not be able to get the custody.
First be 100% sure of your claims and then proceed with the matter.
If you are of the opinion that your wife may file 498A, then please take an Anticipatory Bail.
Seek the advice of an expert Lawyer at the place where you live. Free Advises on Internet sometimes become an expensive affair as the experts here do not have all the details with them. So it is always better to approach the Lawyer for filing a case.