Yes you can! it will be better to have at-least 2GB RAM and try all in one setup. Ref: all in one

Yes, you can. but don't expect it to be fast.

I wroted a blog post (in Spanish) to show how to use vagrant + virtualbox to have openstack running.

The post with the screencast + vagrantfile is here:

https://pilas.guru/20160418/openstack-mitaka-instalacion-just-for-fun/

I did some on CentOS and Ubuntu VM, Ubuntu is an easer one to play with: if you want to play with Openstack, you may refer to guidelines http://docs.openstack.org/mitaka/install-guide-ubuntu/ (http://docs.openstack.org/mitaka/inst...)

You may just install Keystone, Nova, Neutron, Cinder, Heat and Horizon to start with, note that your VM should have storage size > 64GB, to play with some guest applications.

Good luck

Yes, you definitely can. Here's how I setup my first all-in-one openstack in CentOS inside VMware: http://sajjan.com.np/blog/openstack/. Also, it doesn't really matter which virtualization platform you use until you understand what you're doing.

You can try Mirantis OpenStack. For installation, they have VirtualBox scripts which make's your work more easy.