Can I clean PCB using petrol?
What you can, can not and should not use depends a lot on the board materials (soldermask etc.) and components. Some components, like trimmer pots, might not work well with certain solvents. I have also worked with in-house prototype boards that had a specific type of solder mask that was made for prototyping. The first time I tried to clean a board with that solder mask, the mask disolved because I was using isopropanol instead of water.

If you are cleaning flux residue, consult the manufacturer datasheet to see what the proper solvent they advise is.
You also mention that it is hard to get alcohol where you live. Perhaps non-drinkable alcohol (often they just call it ethanol) can be gotten. Where I live, there is a tax on food-grade alcohol. Non-food-grade ethanol (with additives that make it pretty much impossible to swallow due to taste and vomit-inducing behavior
) can be had for much lower prices.