* Virtual Network: You can connect con-env1 to VNet2 and VNet3 only. This is because VNet1 is in a different region than the container app, which is East US. According to the web search results, you can only connect a container app environment to a virtual network that is in the same region as the container app1. Therefore, VNet1 is not a valid option. VNet2 and VNet3 are both in the same region as the container app, and they have enough available IP addresses to support a container app environment.
* Subnet mask: You should use /28 as the subnet mask for con-env1. This is because /28 is the smallest possible subnet mask that can accommodate a container app environment. According to the web search results, a container app environment requires a minimum of 16 IP addresses in a subnet2. A /28 subnet mask provides 16 IP addresses, while a /26 subnet mask provides 64 IP addresses, a /24 subnet mask provides 256 IP addresses, a /23 subnet mask provides 512 IP addresses, and a /16 subnet mask provides
65,536 IP addresses. Therefore, /28 is the most efficient choice for minimizing the subnet size.