Only accepted and presented papers will appear in the proceedings if they have been uploaded before the deadlines. Published proceedings can be found here: https://ieeexplore.ieee.org/xpl/conhome/1802630/all-proceedings.
The conference proceedings will be submitted to IEEE Xplore® which ensures a wide dissemination of your valuable work. Once accepted and published (which is usually true for this conference), other indexing services evaluate conferences and independently determine what they will index.
A summary regarding the history, reputation, publication, and registration statistics of the IEEE International Conference on Teaching, Assessment, and Learning for Engineering, TALE, can be found here: http://ieee-edusociety.org/sites/ieee-edusociety.org/files/tale-health-oct15.pdf.
The copyrights of the papers are transferred to IEEE (except if it's entirely the work employees of the US or a crown government).
Authors are expected to attend the conference in person to present their papers and share their ideas. If a paper is included in the proceedings distributed on site and is later identified as a non-presented paper, it will still be included in the proceedings delivered to IEEE. However, it will be flagged as "no-show" so that the paper will be archived but will not be indexed or appear in IEEE Xplore. But: Copyright of non-presented papers is still retained by IEEE.