Option 1 -> "Tie up" means to occupy or finalize something, but doesn't convey the sense of being restricted or constrained.
Option 2 -> "Tie on" means to attach something by tying, which doesn't fit the context of imposing restrictions.
Option 3 -> "Tie down" means to restrict, constrain, or limit freedom, perfectly fitting the context of a contract imposing restrictions.
Option 4 -> "Tie with" means to have an equal result with someone, which is unrelated to the context of restrictions.
Hence, Option 3: tie down -> The phrasal verb "tie down" is idiomatically used to express restricting or constraining someone/something with limitations or obligations, making it the perfect choice for describing a contract that imposes too many restrictions on a company -> correct