A contradiction? It literally states instances where stoning can happen and other instances where God was infuriated for man stoning under certain circumstances. You're too vehement in understanding the context because you want to compare it to your violent book.
Anyways, I already answered your second question but don't Muslims claim all of the Old Testament?
Christianity states that the sacrificial laws are no longer needed due to Jesus's sacrifice.
So in reality you're trying to bring Christianity down because you can't bring Jihadism up.
If your problem is with the OT why do you guys continually bash Christianity rather than the Jews?
Is it because Muhammad knew Christianity was correct?