Questions about AVM FRITZ!Box 7590 AX International

I need at least firmware 6.89, but I can't find any information whether it is available on this router...

Hello, I currently have a Sunrise modem. Can I simply replace the Sunrise modem with the FritzBox 7590? I would also like to add a repeater from FritzBox afterwards, as the WLAN is currently in the basement and is not available throughout the house. Many thanks for your support!

Good day I would like to connect an LTE stick to it for an internet backup. Is this possible with this router and what would be the appropriate LTE stick? The router is operated via Starlink.

Somehow it is not really comprehensible to me what the differences between the Edition A/CH and International models really are. Personally, I would have opted for the Edition A/CH based on the description, as it is apparently tailored for use in Switzerland. However, reading the comments, the International model seems to be the better choice, at least the telephony works via Swisscom or UPC/Sunrise. However, I don't know whether this is also the case with the Model Edition A/CH. I just want to be on the "safe side", it looks like you can't go wrong with the Model International, right?

It doesn't work for me, because the box doesn't have a menu or a landline connection (only Internet telephony). The Tel light lights up when you try to call, but a connection is not established.

Can this router also be isdn

Hello all What is the difference between the AX and the AX International version of the Fritz!box 7590 (apart from the price)?

Hello together, Would it be possible to use this router (AVM VDSL router FRITZ!Box 7590 AX International) with a UPC landline or should I only use the A/CH version? Many thanks for your help and greetings Urs