viabtc accepts transaction who has a previous transaction/s unconfirmed but it will not be confirmed until the previous ones get confirmed first
No, it doesn't. Because they ignore those transactions and the accelerator says "Transaction does not exist" if you try and accelerate a transaction with an unconfirmed parent.
You have to go to the start of the chain and accelerate the first one... wait for the first one to get mined in a block... accelerate the next one in the chain... wait for that to get mined... accelerate the next one... etc etc etc...