Depends how you designed it. If you just built a pyramid, with very few internal spaces of any kind, then the highest you could go on Earth would be somewhere above 8 km above sea level, assuming you have the correct geology under you.

Mountains on earth tend to get no higher than 8 km, as higher than that makes them too heavy, and so they cause the whole crust of the earth in that area to sink. If you build just one isolated brick mountain, on a geologically stable area, you could probabaly get a lot higher, as the load causisng the crust to sink would be far smaller than with a whole chain of mountains.

Bricks Vs Motar. Depends on quality. If you use a good, high cement motar, with very cheap, soft bricks, or cheap, sandy motar with engineering bricks, you'll get obviously different results.

If I'm feeling up to it, and John in kansas doesn't do it first, I'll calculate how many bricks you could stack on top of each other before the bottom one crumbles. Not until after coffee though.