Can i use granulated sugar instead of priming sugar for home brew lager?!
Answers: You can but common table sugar (sucrose) is a disaccharide and despite the negligible quantities you add it can still take marginally longer to prime vs. priming sugar (corn sugar/dextrose) given that it is a monosaccharide. If you don't have priming sugar on hand you can use just about anything with sugar in it and it's a good opportunity to experiment with things like honey, brown sugar, maple syrup, and other common things of that nature which may or may not add a little last minute oomph to your beer.
Yes
Yes.
If used in excess, granulated sugar adds "cidery" off-flavors to beer. Using it as a primer won't get you even near the threshold.