If the room gets plenty of light it is OK to grow cacti in it, also it depends on the species you are growing since some genera/species require more light than others to grow properly. If your cacti do not get enough light they will stretch for it and this looks really ugly, the technical term for this is etiolation.
No!
A warm, dry place in direct sunlight but some cacti will be sunburnt by direct sunlight so indirect sunlight is usually used.
Yes: Prickly Pears, Barrel cacti, Saguaro cacti, Aztekium cacti, and Echinopsis cacti a.k.a the hedgehog cactus
cactus for a single plant cacti for plural
All cacti are succulents, but not all succulents are cacti.
Bathroom That's pretty simple...... BATHROOM
We need to remodel our bathroom. Where can one find plain and cheap bathroom liners?
No, mealworms do not eat cacti and cacti do not occur naturally in the Sahara. Cacti are natives to American deserts.
B) For hygienic purposes when you use the bathroom.
There tons of genera of cacti.
Yes, cacti are dicots.
That would depend on where that person is at the time of the need. In most modern areas, that place would be a bathroom, specifically a toilet or urinal in a bathroom. A bathroom with a toilet may also be called a men's room, a ladies room, a lavatory, etc. In places that don't have some form of bathroom facilities, the place to urinate is dependent on the culture of that place.