What is the difference in heat shield requirements and cosntructions for different demands?

For example, in terms of Joules / Kg converted from kinetic and gravitational energy to heat:

1. LEO reentry, 7km/s -> 0, =24.5MJ/kg

2. Escape velocity reentry, 11km/s -> 0, = 60.5MJ/kg

3. Aerocapture, 12km/s -> 11km/s, = 11.5MJ/kg.

4. Aerobraking, 11km/s -> 7km/s, 26MJ/kg

I assume in all these cases most of the heat is transferred to air molecules, and most of the rest is radiated away. Only a fraction is conducted away from the heatshield.

Are the ratios similar for different types of reentry?

Could the Spacex Dragon Heatshield, designed for Case 1 above, be used for Case 4?

Can Case 2 be done as Case 4, followed by a cooling period, followed by Case 1?