Knowing that $3$SAT is NP$-$hard, show that $4$SAT is NP$-$hard

Knowing that $3-$Coloring is NP$-$hard, show that $4-$Coloring is NP$-$hard.

Knowing that Clique is NP$-$hard, show that Subgraph Isomorphism is NP$-$hard

hand written solution please