I've seen this interesting function is under developing.
Is the function designed to ask if the broker allow trading the specific asset or just check if the trade could be entered accordingly the Zorro's internal settings?

Thank You

No, just internal. The enter() functions will ask the broker.

Ok, thank you.
Is there any way to check if an asset is available, without opening a position?

Not directly. You could check the market time. But even in during market hours it can still happen that the trade is not filled due to low liquidity.