Any digital photo is fine, so long as it fits the format, size and dimension required. It might take some juggling about with software to get your photo into shape, and an element of frustration might creep in: but you'll get there!

You get issued with a document authorising your entry, and the issue of the visa. You should make sure you print out a copy of this: it's in their system, they can access it, but, well, this is India

You should head with your paperwork to the dedicated desks dealing with e-visas: though this might be a feature of the busier entry airports. At Mumbai the e-visa desks are at the far end of the immigration hall. For subsequent arrivals on that visa, now stamped in your passport, you can head for the regular visa desks: that, at least is my experience ... but Indian immigration has a capacity to surprise us,