Are cashews good for weightloss?

Maybe not. Helpful weight loss foods are natural foods that take time to chew but contain few calories. Examples include carrots, celery, and iceberg lettuce (without salad dressing). A cashew is a delicious nut, and nuts have protein and fat, which means more calories. Just like with peanut butter, a little is good, but a lot would be bad. A calorie is a calorie, regardless of where it comes from.
Hard to tell. Everything in moderation is okay. There are no "super foods" or miracle foods that help people loose weight. Avoid advertising that emphasizes one food as a successful therapy for weight loss.