Am i Still able to use tools from the old site?

Yeah. The national focus tool is the only one which has been deprecated so far; meaning that it won't have any more updates to it, and if there is a bug it probably won't be fixed.

The country tool is next in line, once it gets added to this site.

A message will appear on any tool no longer supported on the old site. This doesn't mean they won't work, and some people are still using the old tools as they already started focus trees there/are waiting for a new feature here for it to be worth moving over.

Once all of the tools on the old site have been deprecated there will be a countdown for when the old site is replaced with this new one. But that won't be for a few more months, at least.