Full DNS control is not available with free hosting. We provide CNAME record support, and support for MX and TXT records (through the SPF records menu) on the domains of websites we host (so if you’re hosting example.com with us, you can setup MX and TXT on example.com, but not on sub.example.com). That’s all we have right now on free hosting.
If you have your own domain, you can use a third party DNS service to get full DNS control, although then you’re responsible for making sure all the DNS records are correct.
Premium hosting does provide full DNS control, and you can also have your subdomains migrated there.
I can understand that your budget may not allow for premium hosting or buying your own domain name. But please understand that if you require features but are not willing/able to pay for them doesn’t mean we have to give them to you for free. If your budget does not allow for the things you want, you either need to increase your budget or reduce your demands.