Yes you can run seperate Eggdrops on a shell and they can be connected to different IRC networks. However, any one of the Eggdrops can only be connected to one IRC network at a time.
Yes, how many Eggdrops (or other processes) you can run depends on the shell provider and how many background processes you have paid for.
This isn`t suited but its also possible to have two different eggdrops running from one source just add another eggdrop.conf and change the name to botnick.conf then run ./eggdrop -m botnick.conf