You cant enter Georgia via Abkhazie from Russia as Georgia considers it there land which is illegally occupied so if you did some how manager to cross from Russia to Abkhazie then into Georgian at the Georgian checkpoint you would be arrested for illegally entering Georgia and heavily fined so that's that out the question

Even if you enter Abkhazie via Russian then head back into Russia and cross into Georgia via Russia North Ossetia you will have problems, there was a sign stating this in 2013 at the Georgian border, i think the fine was $1000

You can sometimes which i would not 100% rely on enter Abkhazie via Georgia then once in Abkhazie depending if you have a Russian visa cross into Russia but you would need to apply for an Abkhazian and Russian visa before hand and it is also up to the discretion of the Georgian border guards.

After entering Abkhazie if the guards let you cross you can go back to Georgia (if you did not enter Russia and then back into Abkhazie) but will be questions about your trip to Abkhazie by the Georgians however the fact you have a Georgian entry visa and no exit you should be fine after a few questions

My info on this was from the former Georgian ambassador of the Georgian embassy in London who i sat next to on a flight to Georgia a few months ago

You can enter Georgia from the Russian Republic of Dagestan then into Azerbaijan then to Georgia. You would need to apply for a Russian visa & Azerbaijan visa before hand.

For October and the fact you have a 4x4 you should be fine with regards to the weather condition i would 99% guarantee it

However as for land slides they just had a major landslide last year which is not a frequent event so you would think the area that gave way has given way so another landslide would not be as likely this winter so i would also say on October in a 4x4 with the correct Russian visa you would cross the Zemo Larsi border between Russia and Georgia with no problems

I take if you are from Western Europe so another route if for some reason both the Georgian to Russian border and also the Russian to Azerbajian then to Georgia border are both closed which i highly doubt it ?!?!?! just cross from Russia into Ukraine, North of the Kharkiv border which is not currently effected by the current conflict in the East of the country and then head West

Thanks a lot for all these replies,

Another question:

Coming back from Kazakhstan and going to Georgia, when I have to apply for my Russian visa I have to give some towns on my road across Russia.
I think to give Astrakhan, Elista and Vladikavkaz.
Do you think there is any problem to write these towns' names on my visa's application?
(Astrakhan and Vladikavkaz are into borders' areas).
RR.