Sorry for late reply.didnt check in on the thread for a while.
i think this is the usual cng adjustment setting.its hardly a 5min job to be done by an expert cng mechanic but only IF ur cars' throttle body is clean and tappets are well adjusted.if not, u ll need to get that done first (needs to be done every 20,000kms)
The larger round bottle which u stated in ur next post is the one for brake oil. if the sound is always there when u brake and its a squeeling sound (cheeennnn) then u need to change the brake pads on the front wheels.its an easy and cheap job.labour around 200rs and pads from 500rs-2000rs, all qualities do just fine.and do NOT fill the oil before changing the pads, because when u ll put new pads, the brake cylinder will be pushed back and will automatically rise the level of oil in the bottle.however, if it remains less even after that, then u must top it to the max level.
as for the 2nd smaller bottle just beside the larger one, its for the oil for operating clutch.most new cars have hydrolic clutches, which means that its operated by pressure of oil (just like brakes) and not by wires.keep that to a reasonable level too.