Apart from your problem with the line blaster I'd say It's normal as there are sometimes differences between them as they are completely different platforms. levels are made for PC, then are converted to mobile and tablet platform, sometimes slight tweaks have to be made for that to work so there can be slight difference…
To get rid of them you must first get rid of the mesh by tapping two same-colored blocks that are touching them, then use a rocket or other bomb to get rid of them. If your bomb isn't ready when you get rid of the mesh, it will just come back again.