Lying about the Age
Question :

Is it permissible for one to conceal his real age from a group of people even if he is not in danger? Is it considered as lying?

Answer :

Yes, it is permissible to conceal one’s age, as it is not considered to be lying. Lying is giving false information.
Lying about one's age is Prohibited.

Lying
Question :

Is it permissible to lie to a non-believer?

Answer :

It is not permissible.