Spraying the frame of a metal bed is quite tricky. You can use a metal paint primer. Most paint professionals use "Flat paint" as a primer because it mixes with other products. So no worries on the rust preventative enamels and latex enamels.
Without recommending a brand name, look for a premium quality spray paint. A good quality spray paint in standard colors should cost approximately six dollars a can (United States 2012). Be sure to clean the metal surface completely, use a metal primer, then apply several light coats of your finish coat allowing ample time between coats.
Either oil paint or pastels.
metal
Certainly. You may need to sand and "primer" it first to ensure that the new paint color will properly adhere to the metal. This similar method is used to paint cars, too.
If the surface is metal you can. Use a good primer too.
Yes, you are never required to use a frame except for water beds.
Not usually. Most cribs can be converted using normal full size bed rails (if you use headboard and footboard) or a full size metal bed frame (if you are only using the headboard.) See below for a selection of full bed frames and bed rails: http://www.thesleepshop.com/store/pc/Full-Size-c16.htm
Without recommending a brand name, look for a premium quality spray paint. A good quality spray paint in standard colors should cost approximately six dollars a can (United States 2012). Be sure to clean the metal surface completely, use a metal primer, then apply several light coats of your finish coat allowing ample time between coats.
If you need to repair a metal bed frame, it may be necessary to use a welding torch. Be sure you know how to properly and safely operate it by consulting the manufacturer's instructions. Do not repair your bed in the bedroom-- take it outside or into the garage!
Either oil paint or pastels.
Yup
No.
I don't believe you could use oil paint on your car, because it wouldn't adhere to the metal body panels. I would recommend using automotive paint lasting results, or at least paint intended for use on metal.
metal
use your hand and brain
Since we spend so much of our life in bed, having a quality bed is a necessity! The best bed frame to use for three quarter beds, are those made specifically for three quarter mattresses. Depending on your style, there are metal, fabric, wood and leather frames available.
Not especially as with twin beds the sides that are pressed together will simply press into the mattress and cause an uneven night's sleep. Best to just get a cheap king size bed frame - better yet to get a good frame to support the box springs and mattress.