Suspended Ceiling Grid

I need to find out if studs in an open wall are even, or, more to the point, how to even them... I can't use a level horizontally against the faces right? Right do I do? To be clear, I'm trying to find out if all the stud faces line up with eachother, thats what I mean by even. Thanks

Our house was built in the 50s or 60s. The bathroom has aqua color tile half way up the walls all around. We are in the process of remodeling the bathroom. We removed the wallpaper in the bathroom from the tile up. We'd love to remove the tile everywhere except in the bathtub. (Our bath tub has tile about 3/4 the way up. They had wallpaper above it in the tub too and it was getting mold under it. I'd like to take some of the removed tile and use the tile to get the tile all the way up the wall in the tub.) I was wondering how to do it with doing the smallest amount of damage to the tile and the walls. I have a spot in the bathtub that I could use a few tiles to repair a spot that has a nick in it. We'll have to paint the walls underneath it. I'd rather not have to replace the walls when I get the tile off. I guess another option would be to remove all the tile and retile the tub with a color we can find these days. But I bet that's going to add a lot to the cost. If I can find a way to just get the tile off without doing damage and reusing the tile in places I need it, the cost to remodel the walls will be a few cans of paint. So, the biggest question I have is how do I get the tile off with doing the smallest damage possible. Maybe a heat gun?