How many rounds does PikyHost include?

It is stated in your quotation and depends on the scope. Ask sales before the project starts if it is not clear.

What happens if I use all my rounds?

Additional rounds can be added. Your project manager will tell you what that means for scope and schedule before any extra work begins.

Can I see more concepts instead of refining one?

More concepts at the start is a scope decision made in the quotation. Requesting fresh concepts after approving a direction restarts the project rather than revising it.

Is unlimited revisions ever a good offer?

It sounds generous but it usually means the price already assumes a long negotiation, or the work will be rushed. A clear brief with defined rounds gives you a better result.