Yes but it is less likely to happen
Not usually because a lack of period indicates a lack of ovulation. You would need to speak to a doctor about your options if you wanted to conceive.
If your not having periods,the chances are your not ovulating.in which case no.but if your cycle is just irregular then its still possible just harder to pin point ovulation,if your not getting periods discuss this with your doctor,they should be able to help with this.