Donation wallet address I read that wallet/account is not the same as bitcoin address. The address can be used only for single transaction. How do you receive donations on your address? Are wallet addresses unique for the network so that I can generate my wallet in one service, eg. blockchain.info, and used it in different service? How do you call the address of the wallet if not address?
I read that wallet/account is not the same as bitcoin address. 


A bitcoin-wallet is only a way to store multiple private keys (corresponding to multiple bitcoin-address). 


  The address can be used only for single transaction. How do you receive donations on your address?


Addresses can be used for an infinite number of transactions. If you put a donation button somewhere referring to an bitcoin-address of yours, all those donations will get paid to this one. 


  Are wallet addresses unique for the network so that I can generate my wallet in one service, 
  eg. blockchain.info, and used it in different service?


With a wallet (like the bitcoin-core client) you can generate new bitcoin-addresses as well as using other services like blockchain.info. Those addresses are unique and by exporting/importing the private key you can use those addresses in other services as well.