Hello!
I have 2 questions as a beginner!
For our project we made a donation-bitcoin-adress and put it on our website!
We gave the Adress a label.
1. What is if we change the label once (in bitcoin-core and website)!
Is the Adress working right and can we get and see all transactions of the past and future (with old/new label)
or is this a wrong way which makes errors?
Maybe the labelchange is possible and don't break the adress?
The label is not something that goes out to the rest of the network or to the blockchain. Labels are local to your wallet only, so whatever adding a label, changing it, or removing it won't make a difference. Because labels are for your wallet only, you can set it to whatever you want and no one will know or care.
2. I know that is recommend for privacy to choose for every single transaction a new adress.
But it is technical possible to use just one adress for all donations over many years?
Yes, addresses can be reused and there is nothing to stop that from happening. However, it is recommended that you don't reuse addresses.