"got numbers of tokens from it" : What is the average of tokens you can get from an airdrop campaign ?
Do they always and only revert ETH ?
Is it mandatory to get MEW to collect these tokens or blockchain.info is also usable ?
Usually you get equivalent of your stakes. So basically every person who enters an airdrop gets his own stakes. People who organize an airdrop simply put some amount of tokens and that amount is fixed. At the end those people just sum all these stakes and devide the tokens/coins. WHich means less people to enter, more you will get.
There are many ICOs that have their own airdrops, but this doesn't have to be the case. Some ICOs have their tokens on other platforms such as waves and neo, although many are using ethereum for this. Above when some another crypto currency lunches or they want to gain exposure they organize an airdrop - not all of them are token related.
MEW is easierst solution but it is not the most secure one. Blockchain.info support ethereum but doesn't support ethereum smart contracts, at least till now, which emans you can receive your tokens on that address but will be unable to spend them and you won't see it in your blockchain.info wallet but you will have to use some tools such as
http://etherscan.io/. Although you can spend the coins later on by extracting private key from blockchain.info wallet and importing them into another wallet/software such as MEW or any other that can do the job for you.
