Can Y open garage door without myQ?

[Bill D]

The car switches to Wi-Fi when it detects your pre configured Wi-Fi connection to be in range and good strength, which happens as you are pulling close to your garage. Otherwise it stays in Cellular connection. Since there is no Wi-Fi that can reach while you are driving other than a hot spot on your phone the garage or home Wi-Fi and cellular data will automatically switch to the best available signal.

I believe what you describe is only true if "Remain Connected in Drive" is checked (its in your car's wifi settings).

If it is unchecked your car will only connect to wifi (no matter how strong it is) when your car is shifted into "Park".