You could have IP forwarding disabled if you don't want communication between VLAN's. Find below the link for the article which has details about how to stack switches:
How to create a stack with Summit switches
If you have further questions, I would recommend you to open a case with TAC.
The best practice is always use port-based VLAN. Meaning each VLAN should have only 1 IP Segment. To avoid broadcast chaos traffic from different IP Segments within the same VLAN. Even more so if you run multicast L2 IGMP and not L3 multicast.
The design above is very typical of HA. However, the issue is on your Firewall. Is your pair firewall stackable as well ? or running Cluster ? or running just a basic VRRP ?
This requires your stackable switch to be running either L2 LACP to the pair of firewalls if they are HA stack (Active/Active or Active/Passive), or L3 ECMP or OSPF ECMP or etc.
Many things to consider to have a seamless integration with your firewall in HA mode.
Based on the diagram, i supposed that the below are the ones that we need to configure..
1. Configuration of up to a maximum of 18 VLANs total for 4 switches
2. Assignment of ports interfaces to respective VLANs
3. Assignment of IP addresses to respective VLANs
4. Configuration of Management IP
5. Configure Hostname
6. Configure Stacking
7. Configure Link Aggregation
8. Backup Configuration
9. Upgrade of firmware ( If needed for stacking )
But i have one concerns, since one of the vlan will be sending and receiving multicast traffic, what do i need to configure on the switch for multicast traffic to flow through ?