This is an attempt to clarify the special abilities of classes in this world, this is by no means a comprehensive list and it is of course always upto to DM to set the difficulties and such, so take this more as guideline:

Some people can detect unlife reliably: Reann hunters of Journeyman or higher, Iorak and Ra Paladins of Paladin rank or higher. Life followers and priests of Journeyman rank or higher. (Automatic unless hidden, then might require spellcraft roll modified by hider skill) They can also get more detailed information.

In addition those of lower rank in above and any Bishop or higher of any good church can detect huge ammounts of nonhidden unlife, but this is much more unreliable. (much more likely to require spellcraft rolls with much higher difficulties) also the information is usually much less detailed.

Druids and Rangers of Journeyman rank can detect unlife in natural settings with a roll against Animal Empathy(used for all the nature skills)

Iorak an Ra Paladins of Journeyman rank or higher can detect outsiders reliably.

Any Journeyman or higher in any magic academy can detect unlife on successfull Lore roll. (difficulty determined by the level of hiding)

Anyone can detect and try to indentify magic effects on successfull Spellcraft roll.

a full spell user (Wizard, Sorceror, Cleric, Druid) can try to determine the portal's destination with Spellcraft, with difficulty determined by the portal. The response is generally in the form of: local, other plane.

On good success you may get to know more, like if the distance is very far or closeby on a portal to this plane, and the general type of plane if interplanar.

Also the general type or even the identity of the opener might be gained.

Is accomplished by anyone with Search skill. Rangers often get automatic success following easy tracks in nature regardless of skill. Also Rangers are the only ones who can track on hard surfaces, like inside a cave.

Druids and rangers can communicate with animals using Animal Empathy skill. The level of communication is limited by the intelligence of the animal. A hawk will have a lot more to say than a worm, but ofcourse communication may be accomplished with both.

The difficulty of the communication depends on the “closeness” of the other thing, it is for example much easier to communicate with a mammal than with a fish.

The skill can be also occasionally be used to “read” nature to detect ambushes and such from the disturbances.

In general Lore skill is used for these with difficulty depending also on your character. Each race and class has things they know better than others and thus the required roll is lower. For ecample an elf will have much easier time to know about elven history than a dwarf.

Each class has other forms of professional knowledge, these are usually rolled at +1/level + some Attribute.
Few examples below:
Fighters: siegecraft, militaries, weaknesses of enemies..
Barbarians: weakneses of enemies, Raiding tactics ..
Bards: Writing styles, music…
Thieves: lock lore, location of fences..
Clerics: Own church rituals, other churches…