I would like to post a picture on instagram or facebook of a screenshot of a text convo. but i would like to blur or cross out a name or the phone number. what would be an app for that?
There is an app that many of us (Ambassadors) use when we write guides that you can use as an app on your phone or even a desktop version for PC called Skitch and it has a pixelated tool that will do what you want. It's free and works real well.
If you just want to cut the name off the top of the conversation, you could also just open the photo in the stock Photos app, click edit, and then use the crop tool to cut it off.