In this guide, you will learn how to get level 51 Pokemons in Pokemon Go. It will provide you with the secret tips to do so.
There is no level 51 in Pokemon Go but you can power up your pokemon to the strength of level 51 with a trick.
So to take a pokemon to level 51, you first need to reach it up to level 50 and then make it your buddy by collecting the hearts.
When you have made it your best buddy, you will find that it is powered up to CP-3577. From there on, you can take it to level 51.