Read the reviews, compare side by side, and don't forget to factor in Dynamic range. How "clean" your High ISO is is not the only indicator of image quality. For example: Who cares if a camera has clean ISO 6400 if you're usually only shooting at ISO 200-400 anyway?
Yes, but do you really need 52? How much time will you spend selecting one spot, etc?
Hard to say. You're looking for camera that covers everything.
Landscape/Scenery: Usually low ISO. Sharp lenses needed. Nikon and Sony have the advantage here, especially Sony with it's huge resolution and dynamic range.
Macro: All cameras will do well here, and all brands have good macro lenses.
Night shot: Long exposure on a tripod? Or high ISO to freeze motion? 2 very different things. If it's the first, see "landscape/scenery". If it's high ISO shots, the Canon and Nikon will do very well.
animal during travelling: how far away? What animals? Canon has very good, and very big, expensive telefocus lenses (don't underestimate how hard it is to travel with big lenses). Nikon and Sony take second place here, but if you combine an A850 with a 70-400G or a 500mm mirror lens then you have lots of resolution to play with and crop to your liking.
i think the a850 is a pretty good deal if one is buying into a system and does not have any specific requirements to fulfil. most enthusiasts hardly print out their images, let alone to 8x10 or bigger so the noise issue can be mitigated with NR software. it reminds me of the old 5D. very basic camera that churns out good image quality at an attractive price point. the only thing i don't like abt the camera is the design, ergo and menu.