Regarding your questions, you want to offer something in the evening to Krishna besides fruit and milk, so there is no harm. Because Krishna can eat as many times as you give Him to eat, because He is unlimited. He can eat unlimitedly, provided we can supply foodstuff unlimitedly. But that is not possible for us. Therefore, we limit the supply. But anyway, if you can increase the offerings it is very nice. But one thing is that whatever you make routine work to offer Him food stuff, that should be continued. Do not change it. So if you can continue to offer foodstuff like fruits and milk in the evening, you can introduce that system. There is no harm. Your second question, ice cream purchased from the market may not be offered. Because such ice cream contains sometimes undesirable things, which we should not offer. We must offer to Krishna only first class prepared foodstuff, especially made at home. We shall try to avoid as far as possible goods purchased from the market and offer to Krishna. Regarding your third question, morning lecture is also allowed. Lecture is also kirtana, and so as morning kirtana is there, similarly morning lecture can also be delivered. In New York , or even in San Francisco, when I was present I was giving lectures in morning also. So far as girls or boys lecturing in the morning, that doesn't make any difference. Either girl or boy devotees may deliver lecture if they choose to do. We have no such distinction of bodily designations, male or female. Krishna Consciousness is on the spiritual platform. As such, anyone who is a devotee of the Lord, following in this line of disciplic succession, can deliver lecture, on the teachings of Bhagavad-gita, Srimad-Bhagavatam, etc.
Regarding your question no. 4, Gayatri mantra means it is chanted by a qualified Brahmin. A devotee of Krishna is understood to have surpassed the stage of becoming qualified Brahmin, so Gayatri mantra can be chanted by qualified Brahmin, and the meaning of Gayatri mantra is Gayat—Gayat means sin, and tri means deliverance. Gayatri. And mantra, man—means mind, tra means deliverance. So the things chanting which one is delivered from the mental platform is called Gayatri mantra, or mantra. So all mantras are like that, but this is the meaning of Gayatri mantra.