CBSE 12th

There might be very few chances of that, but yes, you could do economics honours even if you didn't have maths in class 12th. But it won't help you because down the line, for a career in economics, you will need to have a strong mathematics base which of course you missed in the two years of your high school.
If you want only a Bachelor's degree in economics, you can take it up, you'll have to work very hard in statistics and other important topics in mathematics and if you are planning on taking up admission on DU, yes maths is compulsory for BA (Hons) Economics from DU. Apart from it, you can try in other universities also but it depends on the eligibility criteria.

Yes, you can do MBBS abroad. From year 2017 Medical Council of India (MCI) has stopped issuing Eligibility Certificates to candidates who are taking MBBS admission abroad on the basis of National Institute of Open Schooling (NIOS) Certificates and Mark sheets and even State Open Schools. This means Foreign Medical Graduate degree of these students will not be valid in India and hence they can not appear for MCI Screening Test, which is mandatory to clear to be eligible to practice in India. However, your degree will be valid in the country abroad from where you decide to study and a candidate can practice there after obtaining the necessary license to practice as a Doctor in that country. Hope this helps you. Be free to share any problem you have. All the best for your bright future!