I had the same dilema several years ago and did some research on the subject. It is not easy to remove the paint. The chemical streapers are expensive and dangerous for the environment. You can use caustic soda for example but then have to rinse it well. Where are all the chemicals going - to your garden, into the drain? Another option is sandblasting but then you might have to seal the bricks as their top layer is likely to be compromised. Another potential problem is that there might be a reason for painting the bricks in the first place - they might not look that good when exposed.

The step has probably also got years of applications of "Cardinal Red" polish on it which was always used on red doorsteps. Don't know what was in it - if I remember rightly it was a liquid polish which was easy to apply with a rag - but Google will probably help you find the right product to help remove it.

Just found this. I am repainting my kitchen and have painted over quite a lot of what appeared to be old textured emulsion. But in the section I am doing now it has become clear that it's old, painted-over paper: this became apparent when I found some that was loose. I have removed the loose bits and I am not too bothered about the resulting unevenness as the whole wall is an uneven mixture anyway which gives a not unpleasing rustic look. My worry is that, while the paper that is left appears to be well stuck down, what came off did so with such ease that the remainder may be less secure than it appears. I have had problems over the years with several aspects of the house thanks to evident botches done by a previous owner: I fear this may be another. The top edge of the paper in your photographs looks very like the cut back edges of mine. Has yours remained sound since?

Have you tried magic eraser sponges. Worked a treat when my boy got wax crayon the radiators which then melted when he was little. I tried everything else including bleach, bicarb, toothpaste, mayonnaise.... the magic sponge worked tho.