A heads up warning - In all of the betas from April 30, 2010 to July 14, 2020, the top speed "Need For Speed" skill was broken, and if set to level 2 of 3 or 3 of 3, most cars would not shift into top gear. The problem was the gearing was increased, but not the power, so the cars suffered from slower acceleration even with the top speed skill set to 1 of 3, and if at 2 of 3 or 3 or 3, even if nitrous was used to get a car into top gear, the car would slow down and shift back into next to top gear.
As for tier 3 cars, they were locked out on May 14, 2010, but players could still get them as rental cars. The tier 3 cars were locked out from June 2, 2010 until July 2, 2010 when the tier 3 cars were unlocked again.
So beta versions before April 30, 2010 would be OK, or the July 20, 2010 head start version would be a good one since the bus terminal ramps were not blocked off until July 27, 2010 version.
Other key releases:
Oct 26, 2010 - last of version 4.0.
Nov 16, 2010 - first of version 5.0, upgrades replaced with performance parts
Dec 15. 2010 - night mode and snowflake 911 added
Nov 16, 2011 - cops removed from free roam
Apr 11, 2012 - free roam chat disabled
May 01, 2012 - ultra performance parts added, last version with skill mods
May 30, 2012 - skill points removed, replaced by skill mod parts