As to the hard to start trouble,remove,clean the carb,especially the pilot jet itself,inspect the electrical connection on the carb for the carb warmer,test it for continuity...Honda carbs are simple to work on,as simple as any other as the major atv manufacturers all use 2-3 major brands of carbs which are all pretty much alike respective to the carbs brands...As to the rear noise...Check the rear brake lever to see if it is releasing properly when you let off the brake pedal,or left hand lever..If not,tear the rear brakes down,and remove the lever,emery cloth the shaft where it rides inside of the bushing inside of the brake backing plate,and then lightly clean the bushing itself,lube shaft,and bushing up with a marine type grease,reassemble,check for free smooth revolving action with zero sticking,or drag,install new brake shoes as the old ones are prolly shot,or crystallized due to dragging,reinstall the drum,and cover,adjust the brakes to barely dragging at all when axle is spun...Remove drain plug from rear differential,drain gear oil,inspect it for bits,parts,metal pieces,etc...If it is nothing more than a little fine metal particles from normal wear n tear,refill it with hypoid 80 gear oil the specified amount by your manual,or go to hondaatvforums dot net,and download the free e manual for your model to find the proper amount if you don't already have it...Whining noise to me sounds like gear lash issues,squealing is more of a brake dragging,dried out,or metal to metal brake noise......