I found the answer, thanks to a comment by @phoog.
The German version of the website says "Der Zug ist vorübergehend nicht reservierbar.", which seems to translate to "The train is temporarily not reservable.".
This suggested that a ticket can be booked, but a seat cannot not be reserved. I tried by going to the end of the process (I realized there was one ...
Below the present (Friday, 6th December 2019) summary:
tickets valid until the 11th can be rebooked free of charge
but only for the same connection
it does not state how or where to do this
unused tickets can be reimbursed
no trains to or from France on strike days, which is expected to be extended
At present (3 PM) it is unclear if this strike will ...
Appropriate tires for driving in winter conditions (snow, slush, ice, frost) can be dedicated winter tires but there are also all-year tires that fulfil the respective regulation.
A rental car with winter tires not explicitly mentioned in January in Frankfurt may have all-year tires, but my guess is that it will anyways have winter tires as all-year tires ...
The third bullet is the important point.
Can I enter Germany as my first entry point now ?
It is 100% OK to enter through a different country to the one that granted your visa. This is totally normal and fine.
Are there any stamping issues associated with that during the Immigration check in on Airport?
No. You have a schengen visa and you're entering ...
Can't really answer for how to change your ticket or if you will be allowed on board with a ticket for a different train, but from Augsburg to Paris, you have the following alternatives you can still book (and thus possibly exchange your ticket for?):
Augsburg 03:57 (in the morning, or night rather) - Stuttgart 05:36 // 05:54 - Paris 10:05
Augsburg 07:05 - ...
As winter tires are legally required (for your rental time), the car rental agency must have them available on their cars - they cannot rent you a car that is not allowed on public streets.
That doesn't mean they have to give them to you for free - and some of them do charge an extra fee for winter tires; could be per day or per rental. You should clarify ...
In general, if a German city name has some qualifier like a river or geographic descriptor (e.g. Limburg a. d. Lahn, Kempten i. Allgäu or Weilheim i. Oberbayern), DB will name the station using the qualifier in brackets (so the above become Limburg(Lahn), Kempten(Allgäu) and Weilheim(Oberbay) – long qualifiers like the last may be shortened). Therefore, when ...
From the description, this sounds more like proof that you are employed by the Ministry of Foreign Affairs and not in itsself a travel document.
This card can used togeather with your passport to all Schengen Countries.
This is something you should really ask your employer and not here.
Carta d'identità M.A.E.
(Identity Card issued by the Ministry ...
The dimensions of the lockers are as follows.
Small locker: 420 x 800 x 273 mm (~ 90L)
Large locker: 615 x 930 x 472 mm (~ 270L)
(https://community.bahn.de/questions/1582543-schliessfacher-frankfurt-hauptbahnhof-aktuelle-preise - please note that this information is from 2018)
If your bags can be arranged into that volume, then you should be fine.
The owner of a parcel station will know what delivery company can use that specific station.
Identify the parcel station(s) you would like to use (they will have names or ID numbers), then email the owners of the parcel station(s) and ask how to ship from Germany to their parcel station. The owner should be able to advise you what shippers use their parcel ...