Hi,
I understand that you can configure from 1-4 and your ISPs can do the MIP/VIP failover because firewall can't control the route for the incoming traffic on the upstream devices(ISPs).
1: for MIP you can consider MIP group as in KB https://kb.juniper.net/InfoCenter/index?page=content&id=KB4189
2: For VIP, you can configure policy based destination NAT.
Thanks,
Vikas