1) it is included
2) is included. Note, it’s GrindELwald.
3) The Swiss Travel Pass is granting free transport to inhabited places only. With a few exceptions, it is not valid on mountain railways. All services from Grindelwald or Wengen to Jungfrau require an additional ticket.
Please see the STP validity map where you can see on which routes it is valid or requires an additional ticket:
Swiss Travel Pass validity map