which is the best and available tools used for VLSI digital design..

i want idea to choose design tool for doing vlsi digital domain project

Are you going to actually fabricate this design? If so,
then you care foremost about the availability of PDK
support (models, rules, etc.) from the foundry. Not all
tool sets will be supported as a tapeout platform. Some
will require that your design be imported, rechecked
with some "blessed" tool set, and any errors fixed on your
end (without the benefit of those tools).

Beyond that it seems that it's the preference of the CAD
organization, pretty much, as far as what you get. The
tools have to be paid for, somebody has budget say-so
and works the deals, and engineers get to live with it.

So you've "what's accepted, where you're headed?" and
"what's provided or affordable" as two questions to get
you going. Nobody but you can answer these, and until
you know, advice won't help much.