Kindly Stranger

The number of card types matters, not the number of cards. For example, Wicker Witch (an artifact creature) along with Catalog (an instant) and Chaplain's Blessing (a sorcery) will enable delirium.

Some delirium abilities are activated abilities of permanents. To activate such an ability, there must be four or more card types among cards in your graveyard. The number of card types is not rechecked as the ability resolves.

Activating Kindly Stranger's ability twice won't cause it to transform back into Kindly Stranger once it has already transformed into Demon-Possessed Witch.