First, different meanings:
Immediately: means immediately; Recently; In a short time.
Long-term: refers to the expected long-term time; Distant time.
Second, the usage is different:
Spot: generally used to refer to the near future, to express commitment and delay for a short time.
Forward: generally used to indicate a long delay in the relatively long future.
Third, the emphasis is different:
Spot: Spot has the meaning of "present" and "present", focusing on the present.
Long-term: indicates that the expected time is long. Focus on the future.