MC Knows or Believes SO is Dead (Not Brief) + SO Returns

One ML actually dies and remains dead for 13 years.

His spirit is summoned and takes over another body - effectively resurrecting him.

The other ML believes the first ML is dead, but does not give up hope that his spirit will return somehow. He worries that the first ML's spirit will return as an angry spirit that other cultivators would destroy instead of pacifying. He protects the first ML's legacy while the first ML is dead.

Neither ML loses his memories and the second ML recognizes the first ML immediately when he returns despite the fact that he's in a different body with a different face (in the novel) or wearing a mask (in the drama).

Both MLs are alive in the end + get a relatively happy ending.

BL.

The FL dies. The ML spends years cultivating the remnants of her spirit so she can be reborn. When she is reborn, she pretends to have lost her memories in order to minimize the ML's pain, because it is her destiny to die again to save the world. But the ML dies in her place and it's the FL's turn to cultivate the remnants of the ML's spirit. In the end they are both alive, have their memories, are together and are happy.

The FL dies and remains dead for something like three years. A cultivator's efforts plus an accident result in her spirit partly returning, but her spirit is tied to the life of another female cultivator. When the other female cultivator is injured, the FL is also injured. During the night, the FL has a visible, corporal form that looks exactly like the other female cultivator. During the day, she is invisible. The ML starts to recognize the FL relatively quickly after her return.

In the end, the ML, the FL, and the SFL all have their own bodies and memories, are alive and are happy.

The FL fakes her death (her friend takes her place and does actually die). The ML "knows" that the FL is dead, but never 100% fully accepts it. He suspects that the FL (with a different face) is the FL, even though she denies it, for a long time. 

The ML believes the FL dies, not knowing that the version of his wife that he fell in love with was basically possessed by the soul of an immortal from 500 years in the future and when his wife died her soul returned to her original time. He spends 500 years looking for her soul in the river of the dead before joining her immortal sect and reuniting with the FL. 

The FL is able to resurrect the ML after he is dead for only a few days.

The FL is presumed dead for months before the ML finds her.

ML disappeared for 4 years and is presumed dead. The FL had reason to not fully believe it, but four years is a long time.