Just had a professional company install our system...
Doesn't sound very professional from the description you give.
There is no reason for the heads to be installed right up against any paved surface. The need to be moved. (But given what you've said so far about this "professional", don't expect him to do it for free).
Every instruction book I've ever read always talks about having the heads of a newly installed system ever so slightly above grade level to allow soil/dirt buildup to avoid sinking them into the dirt (which can quickly lead to heads that don't properly retract).
"Green backflow values" ??? What are you talking about? An irrigation system should have a backflow preventer (to avoid irrigation water from contaminating your drinking water... assuming they come from the same source). As for the On/Off valves, they can completely buried and function just fine... but it makes for a maintenance headache if anything every has to be done to them. If you are somehow referring to anti-siphon valves (sort of valves with backflow preventers combined), then the anti-siphon part can not be covered and must be about 1' higher than the highest sprinkler.