do they allow you to transfer the domain elsewhere if you leave them or want to use it elsewhere

That would depend on their policies.

We can't say for sure without knowing what registrar(s) you are talking about exactly.

I wouldn't go near a hosting account with free domains. You are asking for trouble. Pay for the domains like regular folk and be safe in the thought that their yours.

Well, the only time I've got a free domain was from Dreamhost. I decided to make an exception for my rules (http://domaindiary.net/2006/05/25/never-let-your-hosting-company-to-register-your-domain/), but I thought 'what the heck, they are ICANN accredited; I'll register LLL.org for free and transfer it out after 60 days'. Everything went VERY smooth. However, this is DreamHost, as opposed to those OneManShows and GarageOperations...

You have been warned!!!