No. You don't have to have an SD card to get apps. But it might be different for different tablets.
No, if you get them from Google Play you do not need a credit card.
No, but it depends if you have data
you need to download apps. Make a folder in your root of SD card name it "apps". then download your apps here http://wiibrew.org/wiki/List_of_homebrew_applications
Just use the "Google Play" - market app which is installed by default. You'll need a google-account to use it ;-)
You need a credit card or a debit card to pay for apps.
You need a emulator that acts like a google tablet or phone. Bluestacks works well for this. You should try it, but it will be slow down your computer/tablet speed.
You can upload all appliations such as Facebook and Viber on the Surface Tablet. All you would need to do is go to the App store in order to download the apps.
If you need more memory space for additional apps, delete unnecessary data, such as emails, notes, images, music, and any apps you really don't need. This answer should also apply for any smart phone or tablet.
That varies from tablet to tablet. Check the manual for details.
I have a Samsung tablet with many factory apps. Most of which I do not use or don't know what they do. I would like to delete those that I don't need. How can I know what is what?
You do not need a credit card to go to the android market. You do need need a credit card if you want to buy paid apps. You do not need a credit card for free apps.
All android apps can go but it depends on space available on your android tablet. If there is not enough GB of available space then it cannot go. Its highly unlikely you could fit ALL android apps on a single android tablet. You would need way to much storage. But you could download every app at one time or another and delete some to make room for more.