Funding opportunities for roof renovation obligation

Hello everyone,

we are considering buying a single-family house, timber frame construction built in 1987.
The roof is converted but not insulated.

My question:

[*] If I understand correctly, we have to renovate the roof within 2 years. What does that mean? Just re-roofing or just insulating or both?
[*] In which case is photovoltaic required? In every case?
[*] What funding opportunities are available for this?
[*] Is my brother (a roofer for 25 years) allowed to re-roof this for me or MUST I have it done officially by a company with an invoice?

Thank you very much for any help!

Regards
Andreas

I can no longer edit the post, therefore the addendum:

The house was built in '76, not '87, and it is located in Baden-Württemberg

1. You do not have to renovate but only insulate the roof or the top floor ceiling. But where there is no plaintiff....

2. I am currently facing the same problem. As soon as you renovate the roof, since this year in BW, photovoltaic panels must be installed.. But there are also hardship regulations etc. Just read about it online.

3. For insulation Bafa BEG individual measure. For photovoltaic there are special loans in BW via L-Bank.

4. If you want funding that could be problematic, although recently own contributions seem to be funded again, but I don’t know exactly.