I think, Its not a good idea to travel the home country on OPT, if you want to return while you are on OPT. I heard of some people who got rejected to reenter US on OPT. However, if your employer has filed the H1 for you which isalready approved by the time you go back to Nepal, then it is possible to come back with H1 visa. Keep in mind that you can not enter US on H1 visa more than a month earlier of your H1 start date.