As many people get confused about this achievment, I decided to create an effective guide to it. Actually, you can't play with Jahn as the Party Leader, but its a very funny nod to ostalgia.

First, to unlock it, you must play with all 3 difficulties, plus Gorbachev's call. Don't select the sandbox mode, or else it won't work. Secondly, to get this achievment, you must have the genetic techonologies researched, as well automation. You must fully implement the automation of economy, and upgrade all farms.

-When you start the game, immediatly start allowing more and more freedom each month; don't change party or economy through the sliders. You must achieve 'liberal freedoms' via sliders and speeches (always choose to fight dogmatism).
-You also must achieve one party. The fast option to do so is issuing a ban on each party. Do that with caution, preparing before banning a party. Take your time and don't ban more than one party in the same month. It will make the party and people very unhappy; to please the party, send gold to a swiss account.
-When you automate and build the cyber sim via the two events after finishing the automation tech branch, your economy will be ready to unlock the event. You must not change it to market or planned economy. You don't need market economy or khadarism to get the achievment. Changing the economy will prevent you from accessing Jahn.
-Klayber must be the second secretary; also, I usually pick the other more liberal secretary in order to get more freedom - but that's not a must.
-The USSR must exist, so you should finance it and the hard liners. If Yeltsin starts to gain ground, it's almost collapsing; you must support radical conservatives against him via event. Helping Affeghanistan and the socialist camp do wonders too. If you get the SOYA tech, use it to help the socialist camp.
-Party unity must be under 66. Take care because if drops too low or ostalgie gets too high you gonna get some nasty events; losing your Stasi is a real disaster.
-You must have more than 15,0 in your budget. Create revolts and then sign agreements with african and asian countries; that should help you.
-Keep Hoenecker during the first event. Keep good standing with USSR and the Party united in order to avoid the second event while you're not ready.

These are the necessary conditions for you to achieve it. I advise you to try to eliminate Deng Xiaoping and bring China and the ex-members from COMECON to your new alliance. Try to keep them at the social-democratic arena, or else they gonna join NATO and then its a nightmare. Build lots of agricultural and factories in order to get money and standart of living. Latter, use military bases and Stasi to reduce ostalgie. Lots of research centers and eletronics are a must; you must achieve your techs fast. Keep your party united and USSR happy, or else the second event to pick the new leader will flag before you're ready. I had to keep Hoenecker to 1991 in order to get the achievement. Maybe its possible to get before it, but I would say not earlier than 1990 and was damn hard to get even in 1991. Don't care about peace and NATO, they won't have an influence here. Events are a great way to get you back on track: make good use of them. One way to please the USSR is to open the borders when the events come; just hold to your ostalgie, because it can skyrocket. Paid departure is a good way to get money, but just do it during events. Don't tear down the wall, nor allow peace talks with the FGR; doing so will bing a incredibly high ostalgie, and peace talks would change your system to social-democratic and thus not allowing to get the achievment.

Hope this help you commrades. I found it to be a really funny secret; it took me time but I laughed so hard. If you do have any doubts, please comment.