Hello, am going to Seoul from Beijing, Terminal 2 and after 3 days from Seoul to Tbilisi, Georgia

Yes, you can save your luggage in T2 and the charge stand is as follow:

20 Within 24 hours for the luggage with its length, width and height less than 65 cm
30 Yuan Within 24 hours for luggage with its length, width and height less than 200cm and more than 65cm
50 Yuan Within 24 hours for luggage with its length, width and height more than 200 cm

The left-luggage counters are near gate 9 in the arrival hall on the first floor and gate 10 and gate 8 on the departure hall on the second floor.

but I have one problem. I tried to call and ask airport hotline but they couldn't answer. from Seoul to Georgia, I will transfer in BJ right, but I will be in transit zone , I just want to know if I will be able to take back my luggage from where I kept . ( take into consideration, I won't have chinese visa anymore when I will transfer in BJ. ) but anyway I need to check in again in BJ, so hope won't be problem.

thank you in advance if u can answer to my question

Hi, you can get out of the transit zone to take back your luggage if you apply for the stay permit. If you get out of the transit zone, your luggage needs to be checked again when board the next flight.

but should I apply for that stay permit in advance here in Beijing? :/ and aboit checking , in Beijing anyway I need to checky luggage again, its big transfer, 15hours. and I know I dont need transit visa. in this case still I meed that permit?
thank u for ur concerning

Yes,you need a stay permit. You can complete the "embarkation/disembarkation card", together with your travel documents, boarding pass for the onward connecting flight and travel itinerary, go to the inspection counter of China Immigration Inspection to apply for 24h stay permit.

thank u so much :))