You can fill the spaces up in a regular campaign match and invite them in or you can do competitive play in the FREEPLAY section which has the bot aspect checked off.
Not really. When you enter the game, usually the server is already completed and my friends get the message "server full".
? There is no such thing as bot aspect in Freeplay mode. There are two modes without bots: Competetive and Old Skool, but still can not join to them with team, because the options for Friends / Invite only are inactive.