Preventive health checkup under section 80d

Hello

I have some queries on the Preventive Health checkup benefit under Section 80D.

1. How much is the limit for Parents above 60 years (sr. citizens) - is it 5000 or 7000?
2. Is this amount over and above the limit of 35000 for Sr. Citizens? Means is it 35000 + 5000/7000 OR is it included in the 35000?
3. Is a doctor's prescripttion needed for the checkup?

Thanks in advance

Vikas