1. Go to SteamDB[steamdb.info] site, open CS:GO depots[steamdb.info].
2. Open manifests of depot 731[steamdb.info] (or 2347770[steamdb.info] for CS2) and find the one you need based on the date.
3. Open manifests of depot 732[steamdb.info] (or 2347771[steamdb.info] for CS2) and find manifest with the same date.
4. Open steam console (type steam://open/console in browser) and type two lines in it:

• download_depot 730 731 (YOUR 731 MANIFEST ID)
  
• download_depot 730 732 (YOUR 732 MANIFEST ID)

Or for CS2:

• download_depot 730 2347770 (YOUR 2347770 MANIFEST ID)
  
• download_depot 730 2347771 (YOUR 2347771 MANIFEST ID)

Wait for a downloading. When the it is complete, two lines will appear about the end of the download.
5. Go to (YOUR STEAM PATH)\Steam\steamapps\content\app_730 and move depot_732 folder content to depot_731 (merging folders).
6. Run csgo.exe, cstrike15.exe or game\bin\win64\cs2.exe and play!

NOT ALL versions can be played with VAC secure because of digital signatures! CS:GO will be reinstalled!
1. Go to (YOUR STEAM PATH)\Steam\steamapps\common.
2. Rename an existing Counter-Strike Global Offensive folder to other name (For Example Counter-Strike Global Offensive New).
3. Move depot_731 folder to (YOUR STEAM PATH)\Steam\steamapps\common and rename it to Counter-Strike Global Offensive.
4. Launch CS:GO from Steam and play!
5. After playing don't forget to rename the folder back.

One of the ways is to make a server.
In the same way download needed manifests for depots 731[steamdb.info] and 740[steamdb.info]. Then drop their content to new folder.
Configure and run server using command line like in this guide with -insecure launch option.
Ask friends to connect to you using connect (YOUR IP):(SERVER PORT) command. Server port is 27015 by default. You can change it with -port launch option. If you have this port forwarded you can use your real ip. But most likely it will be easier to use programs like Radmin VPN[radmin-vpn.com] or Hamachi[vpn.net].