Re: Noise.
My Decker is in Soybucks on the other side of town, chilling and hacking a host to support his team. The target host is sitting next to a Jammer 6. Does my Decker receive +6 Noise?
A "host" can not sit next to a jammer. A "host" is not really a physical location.
But if a device (such as a security camera) is next to a rating 6 jammer then you can't hack it wireless as the item currently lost its wireless functionality due to high noise that is not generated from distance (unless you can reduce the jammer rating with enough noise reduction to get through. data jack provide 1 point of noise reduction. signal scrub program provide 2 points of noise reduction. you can get noise from a RCC, you can also get noise reduction with RCC with electronic warfare on the fly).
...and the camera can't wireless send his live feed, either.
You can still hack the security camera with a direct cable (this ignore noise, direct connection p.232). If the security camera is part of a host, then you can first hack and enter the host and from there hack the security camera (as you will don't get noise interference when hacking from inside the host. pans and wans p.233)
As above, but he is instead trying to hack something inside a tunnel. Does he receive the Noise for the target being in a tunnel?
A tunnel does not really increase noise, not as long as there are other wireless devices that can route your traffic (a car tunnel have - for example; lamps, gridguide, vents, emergency stations etc etc).
If the target device is the only (or one of very few) devices in a an abandoned underground area you would get some +3 noise (according to the table on p. 231)
Lets swap this around.
My Decker, still in SoyBucks, is hacking that host. Lets say the Jammer was disable. A random parade starts outside. Does my Decker receive the penalty for the parade / event despite the target not being anywhere near it?
Yes you do.
here is a book example of that: If you use your deck as a jammer "Jam Signals" you will increase noise for everyone hacking "by or targeting any devices within 100 meters." p.240
same thing here. if you hack from a device that is located near the parade (your cyberdeck) or if the target you are trying to hack (the security camera) is close to the parade = you will get noise.
if there is a parade between you and the target, then you will not suffer noise, as your signal will be routed to and from the target through devices located in less noisy areas.
also, you get +2 noise if you hack from within the public grid (and everyone with a SIN that belong to low lifestyle or less always start out in the public grid - you need to hack your way to another grid to avoid this penalty). you might also suffer another penalty for hacking across grids if you are on one grid and your target on another.
you never suffer noise or grid penalties for defense rolls.
A satellitelink will limit noise due to distance to -5.