It's best to be honest right now with them. Tell them why you were not honest with them at first. Lay it all out and explain to them that you care about them, that's why you are telling them the truth, that you are sorry that you lied and that you did not expect that you would be getting close to, caring about, and potentially hurting a person online. They deserve that if you really do care about them.

Many people have relationships and feelings, even fall in love with people they have not met in person yet. That's why there is the whole Catfish series. People have been falling in love through written letters (then phone calls) for centuries, long before the internet.

No, you're not too old to have a crush like this. No such thing.

10 years is not always that big of an age gap. It depends on the individuals involved.