If they are starting a potentially very long duty day ( perhaps 12 hours or more, both for long haul and also for shorthaul due to the fact they often do multiple sectors) I can promise you the crew will most definitely not be arriving "4-5 hours early", much more likely to be 90-60 minutes prior to their first scheduled departure of the day, the exact requirement will depend on the airline. Most of my short haul colleagues are very good at timing their arrival for report to the minute, especially if they are reporting at some horribly early time in the morning...and most especially if they only came off duty from their previous block of flight(s) some time the preceding evening.
The answer to the rest of your question generally depends upon whether the crew are reporting for duty at base or down route, and may also be dependent on the airline and/or airport.