I would like to know if it is possible to consult older data using orion Context Broker.
EG: I have a temperature attribute and the value is constantly changing (4,5,9,10,30,2). In the examples and specification i had the impression it is only possible to consult the latest value (in this case 2).
Is this accurate? if so is the older data deleted?
It's correct. That's the way in which Orion works, and makes sense for the most of the use cases. Orion is a context broker, so whenever the context changes (and an attribute value is part of that context) then Orion returns the new value.
However, if you want to have historical context there are FIWARE solutions for that. In particular, Cygnus can be used to persist such historical context in several storage backends (HDFS, MySQL, CKAN, etc.). Among these backends, the Short Term Historic could be particularly interesting in your case, given that its provides a NGSI-like REST API interface for getting secuences of values, as the one you are showing.
Please have a look to the documentation on these componentes for further details.