Which one is better – Mahamantra Japa or Mahamantra Kirtan?

Mahamantra Kirtan is Mahamantra Japa.

When is the best time to chant the Mahamantra? Must it be chanted for 108 times only or can we chant as we wish?

You can chant the Mahamantra any time. The more you chant, the closer you get to your goal.

In one of your answers, it is said that five bodies cover the Atman and shattering the five bodies makes one Jeevan Mukta . Can I reach that stage by chanting only Maha Mantra?

Yes there is no doubt about it.

I am devotee of Sri Balaji Bhagavan. i do worship to Him. I chant the MahaMantra regularly. When I chant, my mind wavers. So I have to concentrate it on something. I get confused whether I should meditate on Balaji Pratima or on the Mahamantra. Please help.

You chant the Mahamantra thinking of the divine compassion and love of Balaji Bhagavan. That is the best meditation.

Even while trying to chant the ‘Mahamantra’, my mind wanders, and thinks about how others have wronged me. With such a corrupted mind, how can I let go of the past?

When mind wanders while chanting Mahamantra, understand that it is very natural for a mind to wander as it carries the burden of past tendencies. Allow the mind to wander and when it returns continue chanting. What you resist persists. Do not judge other thoughts as terrible or normal. Instead of fighting the mind, allow it in its way and continue chanting. Soon by the strength of Nama and prayers, mind gets the maturity to let go of unnecessary past.

My friends chant Mahamantra after eating non-vegetarian food. Is it good or not?

Chanting mahamantra is always good

Does Maha mantra chanting also need initiation from Swamiji or it can be chanted anytime? I want to have Swamiji as my Guru while chanting. Does this need initiation or can the Maha Mantra be chanted without initiation?

Mahamantra can be chanted anytime, anywhere and by anyone. However it gives multi-fold benefits if chanted after initiation from a Guru.

I seem to understand that everything else except Nama is immaterial in this world. However I am not able to concentrate on my chanting for a long period of time.

Continuously chant the Nama — as much as you can, whenever you can and leave the rest to Him. He will take care of you.

I feel lazy to chant the Maha Mantra. So I play a Maha Mantra audio CD and keep listening to it. Is it as good as chanting?

It has been said that hearing (‘sravanam’) yields the same punya as chanting the Maha Mantra. That is the reason behind ‘karna mantra’ (chanting the Lord’s Name in the ears in one’s deathbed). However if you slowly practice chanting it, then in due course, you will taste the sweetness of the Maha Mantra in your tongue.

If the word Vishnu means Omnipresent then everything in this world is God. In this aspect, Advaita philosophy is acceptable and easily understandable. Shall I follow this principle along with the chanting of Mahamantra? Or shall I chant Mahamantra alone?

Just chant the Mahamantra. That will indeed lead you to the true philosophy.