Is there support with purchased subscription?
Can we change source code? How it relay to support?
Where I can find subscription cost?
Any links is welcomed.
No you only need a fuse subscription, then you can use JBoss Fuse in production.
For price you need to contact the sales, as they are the only ones that can give you a price quote. They can also explain what a subscription includes and other terms you may want to know about.