STP's growing concerns

There are so many threads on this site. It's both amazing and encouraging but a little overwhelming when trying to find an answer to a specific question. I have questions and I need answers. I hope this finds concise and thorough contributors.
1. During veg, what happens to the plants during the dark period when using a 18/6 regiment? If there is something special happening, and will it be interrupted if I turn on a normal household light to clean and maintain the room? Are the plants as photosensitive to light during veg darkness as they are to flower darkness?
2. What is the best time to water and feed nutrients? Start/end of the light/dark period?
2a. During early growth(24/0) is it best to water/feed at the same time everyday?
3. When is the best time to prune and top the plant? Start/end of the light/dark period? Does this also apply to the time to cut clones?
4. I don't use LEDs but I'm excited about their potential. Are there frequencies that are better absorbed at the start and end of the light cycle? I think more blue during the "morning" and more red at "sunset"? Do the plants prefer the nature cycle?
5. Is there any benefit of non-routine lighting? would there be good stress? Let me explain what I mean. I run 24/0 while sprouting and very early growth with CFL. Then when switching to HPS and a 18/6 cycle. Is there any research or firsthand experience of throwing a couple 24/0 periods in every week.

Gotta go to dinner. I'll get some more questions out there soon.
Thanks for taking the time to read and contribute.

1. During veg, you can use a 24/0 light cycle. That's what I do -- lights on 100% of the time. But it's expensive, and you can get almost as good results at 18/6, so a lot of people do that instead. And you can do anything in between (20/4, 19/5, whatever). However, you do not want a light period shorter than 18 hours.

Since the plant can have as much light as 24/0, it won't matter if you go in and turn on the light while you're in veg.

Flowering is a different story. You want to stick as close to 12 hours of complete darkness as possible, so you don't want to be going in and turning on a light to clean the room.

2. Have no idea. I do hydro, so the plant always has nutrients. I doubt it really matters in soil, but I may be wrong and hopefully a soil grower will weigh in.

3. I top for four main colas when the plant is 5-6 true nodes high. I don't think it matters what time of day you do it.

Don't know anything about clones.

4. Don't know the answer.

5. I wouldn't jerk the lighting schedule around. Just pick your strategy and stick with it. Light issues can stress a plant over time, so I'd just avoid it.

Good luck!