Hardwood Outdoor Covered Porch ?

Hello,

I've got a 1913 Foursquare home with a large front porch in need of redecking. Currently, the deck has tongue and groove hardwood strip that is painted. I want to replace this with the same type tongue and groove hardwood flooring, probably red or white oak. The porch is open on the sides but is covered with a roof. I would like to stain this new porch a medium brown with a satin or semigloss finish. I also considered prefinished hardwood floors but am told that these are mostly for indoor use. A few questions:

Are there prefinished hardwood floors for outdoor use? Not synthetic decking, as the historic district will not allow it.

What considerations should I have for the stain and the poly or varnish finish since it is outside?

Given that it is outside, should I prefinish (stain and seal) the boards in a more temperature controlled environment first, then assemble them?

Can I nail hardwood directly over the joists, as it is now, or should I lay down an underlayment, such as 3/4" pressure treated plywood first?

If I lay down underlayment, should I put felt under the hardwoods?

Currently the direction of the hardwoods is parallel to the long side of the house. Should I change orientation of the boards? For porches, I have seen them run perpendicular to the long side of the house. Is this generally accepted?

Thanks very much for your insight.

Scott