The difference between Tie up and Undo

When used as verbs, tie up means to secure with rope, string, etc, whereas undo means to reverse the effects of an action.

Undo is also noun with the meaning: an operation that reverses a previous action.

check bellow for the other definitions of Tie up and Undo

Tie up as a verb:

To secure with rope, string, etc.

Examples:

"Don't forget to tie up your hair before you bake."

"The robbers tied up the bank employees before forcing a way into the vault."
Tie up as a verb (idiomatic):

To occupy, detain, keep busy, or delay.

Examples:

"He has been tying up the phone lines for hours now."
Tie up as a verb (idiomatic):

To complete, finish, or resolve.

Examples:

"I'd like to tie up the project before I leave."

Undo as a verb:

To reverse the effects of an action.

Examples:

"Fortunately, we can undo most of the damage to the system by the war."
Undo as a verb:

To unfasten.

Examples:

"Could you undo my buckle for me?"
Undo as a verb (figuratively):

To impoverish or ruin, as in reputation; to cause the downfall of.

Undo as a noun (computing):

An operation that reverses a previous action.

Examples:

"How many undos does this program support?"