Minecraft like building system

Thats two main questions: "How can I make my player able to destroy the block" and "How can I make my player able to place it back". The first is a lot simpler, just add a script to each cube which checks for collision with the players axe etc and if detected then destroy the object using Destroy(gameObject);

yup that could be one very simple solution.

for the other that would be alot more complicated. maybe placing invisible grids where u can place more cubes.

or making the verysame cubes add more grid for example if u place a cube u can place more around the same cube.

thats one idea i leave the code to you hope i helped a little