1) can i cancel transaction Before get verified ?
No. If you've sent it, you've sent it. However, some wallets allow you to use Replace By Fee (RBF) in which you can replace your transaction with a new one that has a higher fee. If you're using Electrum for example, you can decide to enable replaceable transactions.
2) Best pools to speed up "transaction accelerator" ?
AntPool and
ViaBTC.
3) what can Do if i send low fee with Blockchain.info ?
The same thing that you would do with any other wallet.