I wired Shelly 1PM Gen4 as displayed:
But, the light flickers and turns off and on by itself.
I hope someone had experience with this, I need 16A relay here, but now I am worried if Shelly is the right solution. Thanks!
Disconnect it!
O is output of the relay and it’s connected to L when relay closes (turns on).
That is the contact that gives L(switched) to the light.
You need all 3, L and L(switched) and N wires, to use that Shelly.
Where is your load connected to the shelly?
I want to know how switching line to neutral doesn’t blow the breaker…
If there is breaker, it trips. If there’s not, there’s smoke.
But probably it’s not neutral, just blue wire for L…
In any case OP should think twice if he should do this wiring by himself.
Well the Shelly thinks it’s neutral, except when it’s flashing because it’s the same level as line I guess.
Let’s say it’s trial to make standard Shelly as no-neutral one…
I just wonder why it states “wiring correct“ ?
- Blue is N (neutral)
- Brown is L (live)
- Black is Lamp
I can see the brown in the junctionbox, but not connected? 
Thank you for your replies, it’s been disconnected just after taking this picture, and I will not play with it - I was wrong to think I have all the wires.
Thank you - I updated the title, just in case someone might read only it.
Have a look if you have all wires needed where the actual load (lamp?) is…
This is all I have: live (black), neutral (blue) and (unused) ground. I now know I need one more neutral, since the one I have goes through the load. So, basically, I don’t have a neutral in the switchbox here 
Luckily there are lot of no-neutral alternatives around nowadays.
That’s not a neutral. That’s a blue wire being used for the switched live.
Like @Karosm said, you need to be looking in the ceiling rose, not the switch. Either that or get a no-neutral version (and an electrician!)
Indeed. Learned a lot. Thanks!