Invulnerability Effect of Zelda/Sheik's Transform

My friend and I have been arguing about whether or not using transform grants any sort of temporary invulnerability to attacks in Melee.

According to the wiki, invulnerability occurs because the game has to load the characters. However, the wiki states that for Melee specifically:

In Melee, both Zelda and Sheik are loaded in the game's memory at all times, allowing the transformation to occur instantly with no loading required.

This would lead me to believe that no such invulnerability exists when using transform in Melee, though my friend still adamantly claims to have used the transform ability to dodge attacks.

1) Does this invulnerability work in Melee?

2) If it does not work in Melee, what are its mechanics more generally in the Super Smash Bros series (eg how many frames are you invulnerable, how useful is it in practice, etc.)

I'm happy to make this 2 separate questions if necessary, though I think they are sufficiently related to allow them both being tackled here.