Godot 3 and 4 class with handy verification of mobile platform and version given that platform.

PlatformUtils.gd

class_name PlatformUtils
extends Object

#OS Possible values are: "Android", "iOS", "HTML5", "OSX", "Server", "Windows", "UWP", "X11".
const OS_ANDROID = "Android"
const OS_IOS = "iOS"

static func isAndroid() -> bool:
	return OS.get_name() == OS_ANDROID

static func isIOS() -> bool:
	return OS.get_name() == OS_IOS

static func isMobile() -> bool:
    return isAndroid() or isIOS()

static func gameVersion() -> String:
	if OS.get_name() == "Android":
		var export_config: ConfigFile = ConfigFile.new()
		var err = export_config.load("res://export_presets.cfg")
		if err == OK:
			var code = export_config.get_value("preset.1.options", 'version/code')
			var version = export_config.get_value("preset.1.options", 'version/name')
			var resultVersion = "%s %d" % [version, code]
			print(resultVersion)
			return resultVersion
		else:
			print('[engine_root] Error open export_presets.cfgs')
			return "undefined"
	elif OS.get_name() == "iOS":
		var export_config: ConfigFile = ConfigFile.new()
		var err = export_config.load("res://export_presets.cfg")
		if err == OK:
			var version = export_config.get_value("preset.0.options", 'application/version')
			print(version)
			return version
		else:
			print('[engine_root] Error open export_presets.cfgs')
			return "undefined"
	return "beta"