You don't need to worry about your plates closing, as you will face the far larger problem of MK being diabetes in a bottle
Agonizing the ghrelin receptor or increasing ghrelin levels to increase GH production should be avoided (only usecase is if you need it to eat more, which you don't). As this is how MK677 works, it is one worst choices for increasing GH
Unless you can afford to run 8+ IUs of HGH every day and ancilliaries (metformin) for years (which you don't at 13), dont use anything
Use the money you have right now to buy good food and make sure to get the basics (diet, sleep, training, supplements) down as you are still in early puberty, then save money and use it to start GH at 15 if needed. CJC no dac is the only alternative to GH that should be considered and it probably will at best have a +1in increase on final height