If a defendant is unconditionally released from jail because of a preliminary hearing did not take place in the 48 hour timeframe, does this mean all charges are dropped?

Typically you must be charged and arraigned with a criminal offense within 48-72 hours before you are to be released from custody/jail. In most States, preliminary exams must take place within 14 days of the date of arraignment. In your case,it appears that you may not of been arraigned within the proper time frame, which means that no criminal charges have been filed against at this time. You will want to contact a criminal defense attorney in your area to discuss your options and to see if any warrants or criminal charges are pending against you.