[dhilip ravichandran]

If the answer is yes, is it advisable to download and use preview version safely?

[Inkling]

It is, but don't use it on your regular phone. You can if you want, but there are many risks, and I'd advise against it.

[Laura Knotek]

Yes, it is available. Windows 10 Preview: Only these Lumias are eligible for today's release | Windows Central

You should read this article before deciding to install it, though.

[Harrie-S]

It's your phone so it's your call.
But if you read the articles than it's not advisable to install it on your daily phone.
Furthermore if you install it please check before you do it if you can rollback . So install the roll back software on your pc and check if it works.
So please read the articles in WC and make your decision.
Microsoft needs people to install it so they can use the feedback to improve windows 10 but they do not want that people install it on there main phone because it may prevent you from calling due to bugs. (known and unknown)
.