I wonder if I can create a single blockchain account (universal account) that several donors use it to deposit their donations.
Of course, just choose a random private key, generate the corresponding address and publish it.
I don't need to know who he is. So it is not worth creating a blockchain account for each donor.
You don't need to create any account for any donor regardless of whether or not you know them.
Each donor needs to have their own account, with sufficient funds to donate from.
More seriously, it sounds like your a little confused about how things work.
Forget the blockchain for a moment. Does it make sense to you that several different donors (
senders in the title of your question) will withdraw from the same bank account in order to deposit a donation somewhere? Each donor needs to have their own bank account, and it is obviously not up to you to create it for them.
In short, the scheme is of different donors withdrawing from different accounts and depositing to some other (single) account. You can create that account and ask them to deposit into it, but each one of them still needs to own his/her account to withdraw from.