First, I have to admit that I know nothing about our Earth of how it rotates, and why it rotates. But I doubt what would happen if once earth stops spinning itself. I mean one part is having a constant daytime and the other constant nighttime. It’s complicated but it would be possible to have a huge large massive object that is strong enough to cause the earth to stop spinning or to reverse its rotation or slowdown its rotation. I think there should more possible ways to cause the earth to stop rotating but in my knowledge, I can’t find other possible way. I think this would have a huge effect on plantation and animal lives on the earth, some of which could not survive many days with no sunlight. There would be catastrophs every part of the world too(I have no idea what would that be)..