I have a total of 14 playtest packets. They are May 25th, August 17th, October 29th, November 13th, and December 17th of 2012; January 28th, March 20th, April 1st, April 11th, June 7th, June 14th, August 2nd, September 19th, and October 25th of 2013.
I don't know if there were any others, but those are the ones I have collected on my computer. The first one just had premade classes (basically, the LMoP premades), while the one from August 17th had the class write-ups (as well as the sorcerer people were talking about). Apparently they had the intention of making 10th level spells. The sorcerer also had warlock-like casting. It also looked like sorcerers' hit points would have been based on their origin, and not the class itself (so one would have d8, one would have d6, one may have even had d12).
Monk first appeared in the Nov 13, 2012 playtest. The one following brought the classes to level 20, in which the 20th level cleric had spell slots that looked like: 3/2/2/2/2/1/1/1/1; while the 20th level wizard had a few more: 4/3/3/3/2/1/1/1/1. The barbarian showed up in January 2013. Druid showed up in March 2013, as did the Paladin and Ranger. This is also the test where the martial damage dice went away. In the June 7th pack, cleric's got a Deadly Strike ability that let them roll weapon damage twice/three times and add them together (basically a free crit). Fighters also got it, but could do it up to 5 times.
Packet from August 2nd 2013 got rid of the +1 ASI from class. Also added ASI at level intervals, subclasses, clerics got their powers from domains instead of deities (the reaper, lifebringer, etc), druid wild shapes were still super limited (shape of the steed, hound, rodent, fish), with their powerful shapes (bear, cat, behemoth) going to the Moon druid, wizards were called "Mage" and got Scribe Scroll and Brew Potions as class features, monks had a maximum of 8 ki points, Ranger subclasses were favored enemies, Rogues gained blindsense at level 12 (not sure if that's still a thing). Bear totem barbarians were completely different (when regaining hp from HD, you add 2x con mod at first totem choice, while 2nd totem choice you could expend 1-2 HD to regain hp when you entered a rage).
Bard is introduced in September 19th packet. Proficiency bonus is introduced (before this, you had attack bonus and spellcasting bonus). Fighting style is introduced. Bards were also just a 1/2 caster (5th level spells were their max). October 25 2013 packet expanded the druid shapes to be any beast, but gave examples like bat, triceratops, deer. Paladin gains Oath of Vengeance instead of just being relegated to Devotion.
Those are some of the changes to the classes. Wizards remained called "Mage" in the final packet. Warlock was never in the packets, sorcerer was in the very beginning but was never shown again. All other classes made it into the packets. I don't know how I feel about how the bear totem barbarian was in the packets compared to live. Live is much stronger. I liked the ASI from picking the class, and having 10th level spells would have been interesting. Curious what those spells would have been (they were removed before classes were given all 20 levels). The idea that a sorcerer's Hit Dice were dependant on their origin would have been an interesting mechanic, and I wonder how that would have played out. Their armor and weapon proficiencies were also determined by their origin (the dragon origin had suggested gear of chainmail armor and a greatsword for a weapon). It probably would have been a bitch to balance, though.
