I would like to know if led strips can serve as the main light of a living room (4.5mx3.5m) and if so, what kind of strips and where to put it in the room (along the walls, along the edges of the ceiling,etc).
LED strips could certainly light up a room, but they're unconventional.
I think to get good light coverage, you'd have a few strips in the middle of the ceiling. Whether this would look odd is for you to decide. (Personally, I'd not do it.)
Practically speaking, you'll probably need to have transformers somewhere, so that's a concern.
If you want dimming capability, you'll have to choose your strips for that application.
There are a lot of poor quality strips/transformers out there, so unless you want to make a hobby out of replacing your lights, be careful purchasing.
This varies from product to product, but if you use a long string, you might experience voltage drop from end to end. To prevent this, feed the (+) to one end and the (-) to the other end with a reasonably substantial conductor.
Again, widely variable, but heat buildup is the enemy of LEDs. If you can stick the strips to something metal, that'll help.
On the plus side, strips are relatively cheap, so you could do it and see what you think.