Do these apps apply data charges if i use Wi-Fi?

I have 2g data plan and i have an iphone 4s and i watch youtube and go on instagram and play games a lot but all the apps i've downloaded are free but if i watch youtube videos, go on instagram, and play games on Wi-Fi, will the data charges still go up? Or if you use Wi-Fi, does nothing get the data to increase?

No charges apply if you did all of those that you said with Wi-Fi. If you want to feel safer from the charges, then turn on airplane mode and turn on the Wi-Fi.