Question about alternative polyadenylation
According to a 2011 review1 alterntive polyadenylation sites can be located upstream of the 3'UTR (i.e. within introns or exons).  When these sites are used it results in transcripts missing exons at the 3' end and can force alternative splicing.  This alters the final protein product.

This figure from that paper may help make this clearer.



  Figure 1. Schematic Representation of CR-APA and UTR-APA
  
  CR-APA produces mRNA isoforms with distinct C-terminal coding regions,
  resulting in distinct protein isoforms. UTR-APA produces distinct mRNA
  isoforms with different-length 3′ UTRs but encodes the same protein.
  Longer 3′ UTRs usually contain cis-regulatory elements, such as miRNA
  and/or protein binding sites, which often bring about mRNA instability
  or translational repression. CR-APA, coding region-alternative
  polyadenylation; UTR-APA, 3′ UTR-alternative polyadenylation. Light
  green boxes, untranslated regions; light blue boxes, shared coding
  regions; dark blue and yellow boxes, unshared coding regions; lines,
  introns.


Reference:
1: Di Giammartino, D. C., Nishida, K., &amp; Manley, J. L. (2011). Mechanisms and consequences of alternative polyadenylation. Molecular cell, 43(6), 853-866.