Can a 'free' Bitcoin 'marketing' ad be checked in any way
Yes, this is very obviously a scam. 

For some reason, some people seem to lose common sense when Bitcoin (or cryptocurrency in general) is involved. So here is a really quick way to check if an offer sounds legit: Consider the same situation, but using $USD (or your local currency of choice). 

For example:

It advertised free dollars if you send in dollars, eg they will send you back 10x what you send in from $500 to $100,000!

Does this sound believable? What about:

It advertised free bitcoin if you send in bitcoin, eg they will send you back 10x what you send in from 0.1 to 20 Bitcoins.

(At the time of writing, 1 BTC is worth approximately $5K USD). 



Ask yourself: what business would do well to give away $100K USD worth of anything to random people on the internet?

If it sounds too good to be true it probably is.