How to make sure that screen lock really locks and doesn't allow to do anything?
The soft reset by key combination is an important requirement for modern smartphones. Most phones now ship with inbuilt batteries. So, the key combination which stimulate a battery pull is definitely needed. I don't see any reason for it to be disabled. Rather you should be more careful and not press those keys for too long.

As for the access to quick toggles from lockscreen, yes that's a problem for some. Android developers just went with a setup which works for most people. Most would want to turn on the flashlight, WiFi, change sound profile; etc without having to unlock the phone first. The flashlight toggle for example is very handy when you need it suddenly.

I don't know of any way to disable access to toggles. Also, so far I haven't had a wrong press on toggles because the phones come with a "Pocket mode" something which blocks the touch functionality when most part of the screen is covered. That said, I do wish that they bring in an option to disable access to all toggles and leave it to the will of the user. It can be useful for some.