Habe an den RU-ADR-helpdesk in den USA gemailt (CitiADRRU@georgeson.com). 45 Minuten später kam Antwort, die mir kompetent erscheint. Großes Lob für diese Aktion an den Mitarbeiter von Georgeson.com (vmtl. als externer Dienstleister von der Citibank für die Helpdeskfunktion beauftragt).
Die Antworten in blauer Schrift:

1) In ‘Part 1’ of the form (from the bottom of page 3 to page 9 of the Citi form), do I have to fill in the first part of the questions about DTC Participant (‘Depositary Trust Company’ pages 4-6) or the second part ‘registered Owner’ (page 7-9)?
You must complete pages 4 and 5 in their entirety. Your German bank should provide you with the necessary information. You should NOT complete pages 6, 7, or 8.

2) Page 9: I guess, that the DRs I own are ‘not physical certificates’ - is that correct? Yes, you do not own physical certificates. Citibank will invoice your broker for the cancellation fees.

3) Where should I mention my account number at Gazprombank? On page 10, in field 3 an ‘Account number (12 digits/17 digits)’ is requested - but my account number only has 7 digits. You do not enter your seven digit account number anywhere.
The account number of Gazprombank at the NSD (National Settlement Depository) has 12 and 17 digits. Should I enter those data? YES
If yes, however, I still wonder where my personal account number would have to be entered. You do not enter your seven digit account number anywhere.

4) The next field asks for a ‘Name of Contact at Russion recipient bank’ and its e-mail. Can you go without it? Or with the general e-mail contact of Gazprombank?
It is best to get a contact at Gazprombank so that any questions can be answered; but we can proceed without one.

5) On page 11 it says "A Type S account will be required for ceratin holders...." I have opened a Type C account as this was the advise in other guidance for ADRs. Will Type C be okay for me?
Typically yes. You will need to confirm with Gazprombank and your own legal, financial and tax advisors.

6) On page 11 the last sentence: "DR holder has to certify that the DR cancellation....will not result in a change of beneficial ownership."
Is it enough to state that the DR owner and the owner of the Russian recipient account are identical - in both cases it is me?
No additional form is needed. By signing the DR Cancellation Instruction and Certification form, you are attesting to the Affirmative Acknowledgements on pages 12 and 13.

7) I do not understand, how the form I send to you directly and my order to Consorsbank (my broker bank in Germany) come together at your bank...
Your German bank will need to initiate a DWAC and transfer the DRs to Computershare TA#50156

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Morgen rücke ich dann Consors wieder auf den Pelz ... Und dann wird hoffentlich demnächst aus ADRs wieder Aktien - und zwar auf meinem Konto. Sind allerdings noch ein paar Schritte bis dahin.
Fortsetzung folgt.