I have intervlan routing setup on D1

If i setup D1 as primary for stp and D2 as primary for stp, can i do intervlan-routing..

Sure, there is no direct relation between STP and intervlan-routing. But by the way, setting both to primary will reduce both switches priorities to 24578 (other values on some cases/switches), why do you want to do that? they will still compete to be the root bridge the same way they did before. If you want one of them to be the root, set only one of them as primary, or just leave them to the default setting.

if D1 is down, D2 can take over intervlan-routing..

Yes, but you have to set both of them as gateways, as you said below

In this case, i need to setup DHCP pool for D1 and D2? Since the gateway will be different.

For example,

D1 - 10.1.1.1
D2 - 10.1.1.2

PC1 connected to D1

- IP address: 10.1.1.3 ,
- Subnet mask: 255.255.255.0
- Gateway: 10.1.1.1

if D1 is down, PC1 will need to configure the gateway to 10.1.1.2. --> Do i need another DHCP pool for this?

Yes, As far as I understand in this case, you need two pools per VLAN, one on each switch, but I never tried two gateways before, so not sure how well it performs in a real network.

If i setup D1 as primary for stp and D2 as primary for stp, can i do intervlan-routing..

Sure, there is no direct relation between STP and intervlan-routing. But by the way, setting both to primary will reduce both switches priorities to 24578 (other values on some cases/switches), why do you want to do that? they will still compete to be the root bridge the same way they did before. If you want one of them to be the root, set only one of them as primary, or just leave them to the default setting.

if D1 is down, D2 can take over intervlan-routing..

Yes, but you have to set both of them as gateways, as you said below

In this case, i need to setup DHCP pool for D1 and D2? Since the gateway will be different.

For example,

D1 - 10.1.1.1
D2 - 10.1.1.2

PC1 connected to D1

- IP address: 10.1.1.3 ,
- Subnet mask: 255.255.255.0
- Gateway: 10.1.1.1

if D1 is down, PC1 will need to configure the gateway to 10.1.1.2. --> Do i need another DHCP pool for this?

Yes, As far as I understand in this case, you need two pools per VLAN, one on each switch, but I never tried two gateways before, so not sure how well it performs in a real network.

What is the best approach in the real world environment?