Farming game

Hi guys. I am currently making a horror survival game as my first game to learn my codings and stuff. As i go along, i get familiar with the codings and assets offered by unity. however, horror survival game is common nowadays. I would like to learn more. I am considering to make a farming type game. Harvestmoon type of game. First of all, i would like to ask everyone here, how do i code to play alone my terrain? For example, my player will have to dig the terrain and afterwhich the terrain will change its texture. Apart from that, i have no issue. I would like to know how do i make changes to terrain like how i stated. Hope to get your feedbacks and teachings!!

Cheers!

You could use voxels to have terrain that can change completely.

You could have only some parts of the terrain be used as farming- and use a separate game object for those parts.

You could have a prefab of a square of ground in an un-tilled state, then another prefab for a patch of ground in a tilled state. When the player uses a tool on the farmable ground object, you could switch out the object with the tilled ground prefab, and use a particle effect to cover the change.