Can I connect any Thunderbolt 1/2 device to a Thunderbolt 3 adapter? I have a few Thunderbolt 1/2 devices (eSata connectors, DVI/HDMI connectors, etc.) I still have an older device that uses these connectors. Now I'm using a new MacBook Pro with Thunderbolt 3. I noticed that there is a Thunderbolt 2 to Thunderbolt 3 adapter at the Apple store. 

Will it work with any devices? 

I don't want to spend money on a adapter that may not fit my needs, and I don't want to buy all the adapters again for the new format USB-C / Thunderbolt 3. ☺️
Yes, you can use the Thunderbolt 3 (USB-C) to Thunderbolt 2 Adapter to connect your Thunderbolt 2/1 devices to your new MacBook Pro.

From Apple's webpage:


  The Thunderbolt 3 (USB-C) to Thunderbolt 2 Adapter lets you connect
  Thunderbolt and Thunderbolt 2 devices — such as external hard drives
  and Thunderbolt docks — to any of the Thunderbolt 3 (USB-C) ports on
  your MacBook Pro.