Turkish Airlines Miles&Smiles - Connecting at IST Ataturk, and Lounge info

My parents are travelling on Frequent Flyer award tickets internationally from DUB to IST, with a three hour layover at Ataturk and then onwards to IZM - all in Business Class. They have never made the journey before.
Can anyone provide directions on how the transfer works upon on arrival? Are they transferred 'airside' at IZM, and therefore clear immigration at IZM? Or do they have to go landside at IST and change terminals landside? Also, which lounge do they use for this 3 hour period - is the Domestic CIP lounge OK at IST?
Also, on the return trip they are again changing at IST - any advice on this connection - and if there are multiple lounges at IST international departures, which one is best to use?
Appreciate any advice on making the trip straightforward, since they are both approaching 70.
Many thanks.

I assume IZM is ADB, read what is below with such assumption ;-)

They need to pass through passport control in Istanbul (btw, flying in Business they are entitled to a Fast Lane for passport controls. Such invitations are normally given during checkin. If not, they can show their boarding passes in Y and they will be allowed to use the Fast Lane). However, they will collect their luggage at ADB at the international arrivals and pass through customs check there in ADB.

After leaving the passport control, they need to walk to Domestic terminal in IST, ~5 minutes to the CIP lounge. While following the signs for Domestic terminal, they will see the CIP lounge on the left, clearly marked. They need to present their boarding passes. They can relax in the lounge, it is pretty good, except that it can be crowded at times. They don't need to go to gate themselves. For domestic flights, a special announcement will be made in CIP lounge and there will be a minibus taking them directly to the aircraft. That's pretty cool actually.

Hope this helps.

..boarding passes in Y...

Obviously, this would be C ;-)

Is there an arrival lounge at IST? I am looking into a flight which arrives at 6am, yikes~!!

I'm sure the hotel wouldn't let me check in that early, so it'd be nice ot take a shower and get refreshed after a long flight. Anyone know the name/cost? Either I'll fly coach and pay the fee or fly business and get the lounge privledge, thanks.

Head to the hotel, drop off the bags, check out a few sights in the morning before I check into the room. Unless anyone know a hotel that lets you check in early....pls let me know, thanks!

The domestic CIP lounge is quite good. It has a wide assortment of food, wifi. However, domestic lounges do not serve alcohol.