How long can the Vice President act as President when the President cannot perform his duties for reasons of death, resignation, removal or otherwise?

To whom does the President of India address his resignation?

To whom does the President of India submit his resignation?

The President of India can be removed from his post by –

Among the following who has been Speaker of Lok Sabha prior to his Election as President of India ?

At least how many days of prior notice is required for the impeachment of the President of India?