Can two Presence setup instructions place Presence into the same land? (e.g., Shadows Flicker Like Flames putting 2 Presence in the highest-numbered Jungle and 1 Presence in land #5 when land #5 is the highest-numbered Jungle)

Can two Presence setup instructions place Presence into the same land? (e.g., Shadows Flicker Like Flames putting 2 Presence in the highest-numbered Jungle and 1 Presence in land #5 when land #5 is the highest-numbered Jungle)

Yes. There is no requirement that multiple Presence-placement instructions happen in different lands.
In some cases (like with Shadows Flicker Like Flames), this can set up more than two Presence in one land. This extra Presence is generally not immediately useful, but gives some buffer against losing that Sacred Site to Blight, a Blight Card, or an unlikely Event.