WhatsApp calls with background data disabled With Mobile Data and background app refresh turned off, can WhatsApp receive a call while the Wi-Fi is enabled, and the iPhone is connected to a Wi-Fi access point with active Internet connection?

If the iPhone is resting on a table, will I receive a normal WhatsApp call or not? Or will it remain closed, unless I pick the mobile in hand and turn-on the screen.

I will be using my iPhone in another country with international roaming active.
Yes, you will receive the calls on WhatsApp normally, even with the background data turned off as long as you are connected to the Internet (via Wi-Fi in your case).

WhatsApp makes use of a framework called VoIPKit available in iPhone software development kit, which enables it to receive audio/video calls even when in background/not running status or with the device in sleep mode/locked state/screen turned off.