River Surges in Sunlight

If I have one Presence in a land, and I play Entwined Power on another Spirit who has one Presence there, do we have a Sacred Site?
You may target Powers as if you had a Sacred Site there, and they may target Powers as if they had a Sacred Site there. But for all other purposes, no, because Entwined Power only lets you use each others' Presence for targeting Powers - not for anything else, including resolving Powers.
For instance, Gift of Living Energy (a Minor Power) wouldn't count it towards "If you have at least 2 Sacred Sites...", nor would Fear of the Unseen (a Fear Card) treat it as a Sacred Site for scaring away Invaders.
Note that if you Entwine with River Surges in Sunlight, their River's Domain Special Rule only applies to them (read it as "counts as your Sacred Site"). So for targeting, they would treat any Wetland where either of you have Presence as a Sacred Site, but you would still need 2+ Presence as usual.
Tags: Sacred Sites, Presence, Entwined Power, River's Domain (River Surges in Sunlight), 6 more...

If you have a Growth option which lets place two Presence, can you chain them, placing the second one within range of the first one?
Yes, you can do this. In general, after you choose a Growth option, you do everything under that option, in any order you wish. (p. 8)
(Discussion elsewhere) Tags: Presence, Growth, Thunderspeaker, Lightning's Swift Strike, 1 more...

When a Spirit uses a special rule to make a sacred site with only one Presence (e.g., River Surges in Sunlight using River's Domain in a Wetland), do they count as having two Presence there?
No, they still just count as having as many Presence as they have disks in the land.
Similarly, when an Incarna counts as a Sacred Site, it's still just counts as one Presence.
While two Presence is enough to make a land a Sacred Site (as suggested by the iconography), the reverse is not true.
(Discussion elsewhere) Tags: Sacred Sites, Counts As, Incarna, River's Domain (River Surges in Sunlight), 4 more...