Thank you very much for this detailed and enlightening answer. However, this did not alleviate my confusion about the table or xDSL technology in general.
I know some funtionality will reguire non-free code. I do not plan to use the modem for telephone communication. Thus, I will not need FXS (DECT) blobs. Also TP link devices I listed have atheros wlan hardware running ath9k drivers (I do not think I will need to utilize that additional lantiq wave wireless hardware in TPlink 8980 for example) and u-boot bootloader. So there is no problem in wlan hardware and bootloder too.
I do not really care about speed much. So I think I can wait for VDSL for now. I only care about having completely Foss firmware and a decent internet connection.
I specifically asked for cases 1 and 2 because this is where my problem lies. If I reiterate my problem as a question, it will be the following:
Can I buy lantiq xDSL modem and use it in ADSL2+ Mode with fully open source firmware without using its VDSL capability (because VDSL requires non free blobs and ADSL does not according to that table) ?
Or unfortunately, if the device has xDSL modem, one can not use ADSL or VDSL seperately because the xDSL technology requires one unified closed source binary for all DSL communications. Is this the case ?
I look forward for your answer.