Will or Shall have?

Question

1. By this time tomorrow, I will reach my home
2. By this time tomorrow, I shall have reached my home.

Does the second statement improve the first one? What is the exact difference between them and when do we use them? Please clarify.

Answer 1

As with other instances of the use of "will" and "shall" for forming future tenses, the difference is intent versus inevitability, necessity, or obligation.

I will reach home.

Expresses the intent, the desire, the readiness, willingness for the events to develop as indicated.

I shall reach home.

States the fact, essentially. The circumstances are such that, regardless of my desire or often my actions, the future is set, the outcome is known. Barring something extremely unusual or extraordinary, my arrival home is virtually guaranteed.

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Now, in your question you also have Future Perfect (the second sentence). Future Perfect does not require shall. You can say

I will have reached home.

It only says that your intent is to have reached home at some time in the future (a reference is needed in such cases). The actual event of reaching home will take place prior to the time of which such a sentence speaks. And that's the role of the Perfect tense.