And they shall be answered.
I think that is fine, as it makes running the game easier. As long a the effective screenspace for the game itself is a non-standard aspect ratio. If you can, try to avoid putting the UI in the 'black bars' to challenge yourself further.
Ideally it should be built between those times, yep. The idea is to throw together a game in that short period of time (even if it turns out to be not very good - it's about learning!)
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That is allowed, we don't want to stop you building your ideas. But we would love to encourage you to push yourself to more unconventional ratio.
So yes, go for it if that's what you want! But to design the game to incorporate the aspect ratio as part of the play would be really cool.
Well the internal framebuffers for those consoles might not be in a common aspect ratio but since they are made to be displayed on 4:3 TVs they don't qualify.
We don't really want to enumerate aspect ratios that are not allowed. Generally speaking you either make something that's square, longer than widescreen or in a tall format such as in arcade cabinets. The idea is to make something where it is clear it's not a standard resolution so making something in say 4:3.2 would defeat that purpose ;)