What is DNS behavior on mobile devices connected to an untrusted network, and what attack is possible when DNS responses are not validated?

• A.D) DNS responses on mobile are always validated using the device's SIM certificate, preventing spoofing on cellular and Wi-Fi networks.
• B.B) iOS and Android always use Google's 8.8.8.8 DNS regardless of network settings, making DNS spoofing impossible.
• C.C) Mobile apps communicate directly via IP addresses hardcoded in the app binary; DNS is only used for the initial app download and not for runtime connections.
• D.A) By default, mobile devices use the DNS server provided by DHCP on each connected network; without DNSSEC validation or DNS-over-HTTPS/TLS, a rogue DNS server or DNS spoofing attack can redirect app traffic to attacker-controlled IP addresses, bypassing hostname-based security controls.