Could a TU land on grassland (+trees and bushes) on a slope? As an emergency landing?
As stated above, the Tu-154 (as well as all Russian civil aircraft) was basically
a bomber turned into passenger plane.
If anybody remembers the original Tu-134, the Il-76 they all have a s.c. "navigator cabin"
in the nose part, which is actually the bomb operators aiming cabin.
Also the gear was over-dimensioned to allow landings on auxiliary
airfields, grass strips in case the main base was destroyed.
Good proof is the landing of the Il-62, even bigger and heavier than Tu-154
in Germany on a grass runway of just 1000m without a scratch.
YouTube - IL-62 landing on grass
This was really an unfortunate chain of events, that they touched down inverted.
If touching down gear down, even at that speed in the forest,
they would have probably all survived.
See the Tu-204 crash in similar circumstances near Moscow,
mentioned here before.